To repro:
Open the 2D Renderer Samples (master branch) and open the "1 Post Processing" scene. Upgrade the Parametric Light named "Freeform Light 2D". While the newly upgraded light is selected the following errors occur:

ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
System.ThrowHelper.ThrowArgumentOutOfRangeException (System.ExceptionArgument argument, System.ExceptionResource resource) (at <695d1cc93cca45069c528c15c9fdd749>:0)
System.ThrowHelper.ThrowArgumentOutOfRangeException () (at <695d1cc93cca45069c528c15c9fdd749>:0)
UnityEditor.Experimental.Rendering.Universal.Light2DEditor.OnSceneGUI () (at Library/PackageCache/com.unity.render-pipelines.universal@11.0.0/Editor/2D/Light2DEditor.cs:767)
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <695d1cc93cca45069c528c15c9fdd749>:0)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <695d1cc93cca45069c528c15c9fdd749>:0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <695d1cc93cca45069c528c15c9fdd749>:0)
UnityEditor.SceneView.CallOnSceneGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:3615)
UnityEditor.SceneView.HandleSelectionAndOnSceneGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:2741)
UnityEditor.SceneView.OnGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:2432)
UnityEditor.HostView.InvokeOnGUI (UnityEngine.Rect onGUIPosition, UnityEngine.Rect viewRect) (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:425)
UnityEditor.DockArea.DrawView (UnityEngine.Rect viewRect, UnityEngine.Rect dockAreaRect) (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:381)
UnityEditor.DockArea.OldOnGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:371)
UnityEngine.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 parentTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout, UnityEngine.Rect layoutSize, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/IMGUIContainer.cs:346)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr, Boolean&) (at /Users/bokken/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:189)

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GUI Error: You are pushing more GUIClips than you are popping. Make sure they are balanced.
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&) (at /Users/bokken/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:189)

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ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
System.ThrowHelper.ThrowArgumentOutOfRangeException (System.ExceptionArgument argument, System.ExceptionResource resource) (at <695d1cc93cca45069c528c15c9fdd749>:0)
System.ThrowHelper.ThrowArgumentOutOfRangeException () (at <695d1cc93cca45069c528c15c9fdd749>:0)
UnityEditor.Experimental.Rendering.Universal.Light2DEditor.OnSceneGUI () (at Library/PackageCache/com.unity.render-pipelines.universal@11.0.0/Editor/2D/Light2DEditor.cs:767)
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <695d1cc93cca45069c528c15c9fdd749>:0)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <695d1cc93cca45069c528c15c9fdd749>:0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <695d1cc93cca45069c528c15c9fdd749>:0)
UnityEditor.SceneView.CallOnSceneGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:3615)
UnityEditor.SceneView.HandleSelectionAndOnSceneGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:2741)
UnityEditor.SceneView.OnGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:2432)
UnityEditor.HostView.InvokeOnGUI (UnityEngine.Rect onGUIPosition, UnityEngine.Rect viewRect) (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:425)
UnityEditor.DockArea.DrawView (UnityEngine.Rect viewRect, UnityEngine.Rect dockAreaRect) (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:381)
UnityEditor.DockArea.OldOnGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:371)
UnityEngine.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 parentTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout, UnityEngine.Rect layoutSize, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/IMGUIContainer.cs:366)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/IMGUIContainer.cs:676)
UnityEngine.UIElements.IMGUIContainer.DoIMGUIRepaint () (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/IMGUIContainer.cs:543)
UnityEngine.UIElements.UIR.RenderChainCommand.ExecuteNonDrawMesh (UnityEngine.UIElements.UIR.DrawParams drawParams, System.Single pixelsPerPoint, System.Exception& immediateException) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/Renderer/UIRenderer/UIRenderers.cs:132)
Rethrow as ImmediateModeException
UnityEngine.UIElements.UIR.RenderChain.Render () (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/Renderer/UIRRenderChain.cs:483)
UnityEngine.UIElements.UIRRepaintUpdater.Update () (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/Renderer/UIRRepaintUpdater.cs:76)
UnityEngine.UIElements.VisualTreeUpdater.UpdateVisualTreePhase (UnityEngine.UIElements.VisualTreeUpdatePhase phase) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/VisualTreeUpdater.cs:155)
UnityEngine.UIElements.Panel.UpdateForRepaint () (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/Panel.cs:942)
UnityEngine.UIElements.Panel.Repaint (UnityEngine.Event e) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/Panel.cs:985)
UnityEngine.UIElements.UIElementsUtility.DoDispatch (UnityEngine.UIElements.BaseVisualElementPanel panel) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/UIElementsUtility.cs:446)
UnityEngine.UIElements.UIElementsUtility.UnityEngine.UIElements.IUIElementsUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& eventHandled) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/UIElementsUtility.cs:209)
UnityEngine.UIElements.UIEventRegistration.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/UIElementsUtility.cs:74)
UnityEngine.UIElements.UIEventRegistration+<>c.<.cctor>b__1_2 (System.Int32 i, System.IntPtr ptr) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/UIElementsUtility.cs:28)
UnityEngine.GUIUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& result) (at /Users/bokken/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:189)

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The targets array should not be used inside OnSceneGUI or OnPreviewGUI. Use the single target property instead.
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&) (at /Users/bokken/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:189)

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The serializedObject should not be used inside OnSceneGUI or OnPreviewGUI. Use the target property directly instead.
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&) (at /Users/bokken/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:189)

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ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
System.ThrowHelper.ThrowArgumentOutOfRangeException (System.ExceptionArgument argument, System.ExceptionResource resource) (at <695d1cc93cca45069c528c15c9fdd749>:0)
System.ThrowHelper.ThrowArgumentOutOfRangeException () (at <695d1cc93cca45069c528c15c9fdd749>:0)
UnityEditor.Experimental.Rendering.Universal.Light2DEditor.OnSceneGUI () (at Library/PackageCache/com.unity.render-pipelines.universal@11.0.0/Editor/2D/Light2DEditor.cs:767)
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <695d1cc93cca45069c528c15c9fdd749>:0)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <695d1cc93cca45069c528c15c9fdd749>:0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <695d1cc93cca45069c528c15c9fdd749>:0)
UnityEditor.SceneView.CallOnSceneGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:3615)
UnityEditor.SceneView.HandleSelectionAndOnSceneGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:2741)
UnityEditor.SceneView.OnGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:2432)
UnityEditor.HostView.InvokeOnGUI (UnityEngine.Rect onGUIPosition, UnityEngine.Rect viewRect) (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:425)
UnityEditor.DockArea.DrawView (UnityEngine.Rect viewRect, UnityEngine.Rect dockAreaRect) (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:381)
UnityEditor.DockArea.OldOnGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:371)
UnityEngine.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 parentTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout, UnityEngine.Rect layoutSize, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/IMGUIContainer.cs:366)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/IMGUIContainer.cs:676)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Action onGUIHandler, System.Boolean canAffectFocus) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/IMGUIContainer.cs:648)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Boolean canAffectFocus) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/IMGUIContainer.cs:641)
UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUIRaw (UnityEngine.UIElements.EventBase evt, System.Boolean canAffectFocus, System.Boolean verifyBounds) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/IMGUIContainer.cs:607)
UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUI (UnityEngine.UIElements.EventBase evt, System.Boolean canAffectFocus, System.Boolean verifyBounds) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/IMGUIContainer.cs:596)
UnityEngine.UIElements.IMGUIContainer.HandleEvent (UnityEngine.UIElements.EventBase evt) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/IMGUIContainer.cs:529)
UnityEngine.UIElements.CallbackEventHandler.HandleEventAtTargetPhase (UnityEngine.UIElements.EventBase evt) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/Events/EventHandler.cs:125)
UnityEngine.UIElements.EventDispatchUtilities.PropagateEvent (UnityEngine.UIElements.EventBase evt) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/Events/IEventDispatchingStrategy.cs:74)
UnityEngine.UIElements.MouseEventDispatchingStrategy.SendEventToRegularTarget (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/Events/MouseEventDispatchingStrategy.cs:35)
UnityEngine.UIElements.MouseEventDispatchingStrategy.SendEventToTarget (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/Events/MouseEventDispatchingStrategy.cs:26)
UnityEngine.UIElements.MouseEventDispatchingStrategy.DispatchEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel iPanel) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/Events/MouseEventDispatchingStrategy.cs:19)
UnityEngine.UIElements.EventDispatcher.ApplyDispatchingStrategies (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel, System.Boolean imguiEventIsInitiallyUsed) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/EventDispatcher.cs:373)
UnityEngine.UIElements.EventDispatcher.ProcessEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/EventDispatcher.cs:336)
UnityEngine.UIElements.EventDispatcher.Dispatch (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel, UnityEngine.UIElements.DispatchMode dispatchMode) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/EventDispatcher.cs:216)
UnityEngine.UIElements.BaseVisualElementPanel.SendEvent (UnityEngine.UIElements.EventBase e, UnityEngine.UIElements.DispatchMode dispatchMode) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/Panel.cs:399)
UnityEngine.UIElements.UIElementsUtility.DoDispatch (UnityEngine.UIElements.BaseVisualElementPanel panel) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/UIElementsUtility.cs:466)
UnityEngine.UIElements.UIElementsUtility.UnityEngine.UIElements.IUIElementsUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& eventHandled) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/UIElementsUtility.cs:209)
UnityEngine.UIElements.UIEventRegistration.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/UIElementsUtility.cs:74)
UnityEngine.UIElements.UIEventRegistration+<>c.<.cctor>b__1_2 (System.Int32 i, System.IntPtr ptr) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui/Core/UIElementsUtility.cs:28)
UnityEngine.GUIUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& result) (at /Users/bokken/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:189)

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