Steps to reproduce:

1. open a project (tested on URP)
2. go to Project Setting> Shader Graph 
3. Try to change the SG Variant Limit.

Actual results:  The changed result is reverted to 128 and an error is prompted in the Command window:

Expected results: User should be able to change the Variant Limit
{code:java}
NullReerenceException: Object reference not set to an instance of an object
UnityEditor.ShaderGraph.GraphData.GetEdges (UnityEditor.Graphing.SlotReference s, System.Collections.Generic.List`1[T] foundEdges) (at ./Library/PackageCache/com.unity.shadergraph@f393a97dc9bd/Editor/Data/Graphs/GraphData.cs:1311)
UnityEditor.ShaderGraph.GraphData.GetEdges (UnityEditor.Graphing.SlotReference s) (at ./Library/PackageCache/com.unity.shadergraph@f393a97dc9bd/Editor/Data/Graphs/GraphData.cs:1326)
UnityEditor.ShaderGraph.GraphData+GraphDataUtils.ApplyActionLeafFirst (UnityEditor.ShaderGraph.GraphData graph, System.Action`1[T] action) (at ./Library/PackageCache/com.unity.shadergraph@f393a97dc9bd/Editor/Data/Graphs/GraphDataUtils.cs:44)
UnityEditor.ShaderGraph.GraphData+GraphSetup.SetupGraph (UnityEditor.ShaderGraph.GraphData graph) (at ./Library/PackageCache/com.unity.shadergraph@f393a97dc9bd/Editor/Data/Graphs/GraphSetup.cs:16)
UnityEditor.ShaderGraph.GraphData.ValidateGraph () (at ./Library/PackageCache/com.unity.shadergraph@f393a97dc9bd/Editor/Data/Graphs/GraphData.cs:1918)
UnityEditor.ShaderGraph.GraphData.OnKeywordChanged () (at ./Library/PackageCache/com.unity.shadergraph@f393a97dc9bd/Editor/Data/Graphs/GraphData.cs:1844)
UnityEditor.ShaderGraph.ShaderGraphProjectSettingsProvider.OnGUIHandler (System.String searchContext) (at ./Library/PackageCache/com.unity.shadergraph@f393a97dc9bd/Editor/ShaderGraphProjectSettings.cs:83)
UnityEditor.SettingsProvider.OnGUI (System.String searchContext) (at <85775034268147829a57676326841a5a>:0)
UnityEditor.SettingsWindow.DrawControls () (at <85775034268147829a57676326841a5a>:0)
UnityEditor.SettingsWindow.DrawSettingsPanel () (at <85775034268147829a57676326841a5a>:0)
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 <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Action onGUIHandler, System.Boolean canAffectFocus) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Action onGUIHandler, System.Boolean canAffectFocus) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Boolean canAffectFocus) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUIRaw (UnityEngine.UIElements.EventBase evt, System.Boolean canAffectFocus, System.Boolean verifyBounds) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUI (UnityEngine.UIElements.EventBase evt, System.Boolean canAffectFocus, System.Boolean verifyBounds) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.IMGUIContainer.HandleEventBubbleUp (UnityEngine.UIElements.EventBase evt) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEnginef.UIElements.EventDispatchUtilities.HandleEventAcrossPropagationPath (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.VisualElement target, System.Boolean isCapturingTarget) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.EventDispatchUtilities.DispatchToFocusedElementOrPanelRoot (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.KeyboardEventBase`1[T].Dispatch (UnityEngine.UIElements.BaseVisualElementPanel panel) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.EventDispatcher.ProcessEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.EventDispatcher.Dispatch (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.DispatchMode dispatchMode) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.BaseVisualElementPanel.SendEvent (UnityEngine.UIElements.EventBase e, UnityEngine.UIElements.DispatchMode dispatchMode) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.UIElementsUtility.DoDispatch (UnityEngine.UIElements.BaseVisualElementPanel panel) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.UIElementsUtility.UnityEngine.UIElements.IUIElementsUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& eventHandled) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.UIEventRegistration.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.UIElements.UIEventRegistration+<>c.<.cctor>b__1_2 (System.Int32 i, System.IntPtr ptr) (at <d1927dd27a994afa843d6f94be9f148b>:0)
UnityEngine.GUIUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& result) (at <1ba1e436bbd84c1f8d5e08d572f85af2>:0){code}
 

Reproducible with versions: 6000.1.0b8

Not reproducible with versions: 

Can’t test with versions: 

Tested on (OS): 

Notes:

• Workaround: restarting the editor appears to make the issue go away temporarily.