On applying the 'Undo' function over the Prefab Override window, errors thrown in the console. Refer attached video and StackTrace.

Steps to reproduce:
1. Create a new project
2. Create two empty GameObjects "A" and "B" > Drag drop-in project to make prefabs
3. Make B a child of A.
4. Select A > In Override window select B
5. Press 'Undo' or (Cmd⌘ +Z) until Create/Replace Prefab option comes.

Actual result:
Errors are thrown on applying the 'Undo' function over the Prefab Override window.

Expected result:
No errors in the console and Undo operation should perform gracefully.

Occuring in :
2021.2.0a12, 2021.2.0a1, 2021.1.1f1, 2021.1.0a1, 2020.3.3f1, 2020.2.6f1, 2020.1.17f1, 2019.4.22f, 2018.4.34f1

Environment:
Windows10 and macOS 10.15

Stack Trace:
GeneratePrefabOverrides should only be called with GameObjects that are part of a prefab
UnityEditor.Undo:Internal_CallUndoRedoPerformed () (at /Users/bokken/buildslave/unity/build/Editor/Mono/Undo/Undo.bindings.cs:263)

NullReferenceException: Object reference not set to an instance of an object
UnityEditor.PrefabOverridesWindow.UpdateTextSingle (UnityEngine.GameObject prefabAsset) (at /Users/bokken/buildslave/unity/build/Editor/Mono/Prefabs/PrefabOverrides/PrefabOverridesWindow.cs:464)
UnityEditor.PrefabOverridesWindow.RefreshStatus (System.Boolean reloadTreeView) (at /Users/bokken/buildslave/unity/build/Editor/Mono/Prefabs/PrefabOverrides/PrefabOverridesWindow.cs:122)
UnityEditor.PrefabOverridesWindow.OnUndoRedoPerformed () (at /Users/bokken/buildslave/unity/build/Editor/Mono/Prefabs/PrefabOverrides/PrefabOverridesWindow.cs:110)
UnityEditor.Undo.Internal_CallUndoRedoPerformed () (at /Users/bokken/buildslave/unity/build/Editor/Mono/Undo/Undo.bindings.cs:263)

Note: For 2018.4 getting the following errors

1. SerializedObject target has been destroyed.
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

2. ArgumentNullException: Value cannot be null.
Parameter name: componentOrGameObject
UnityEditor.PrefabUtility.IsAnyPrefabInstanceRoot (UnityEngine.GameObject gameObject) (at /Users/bokken/buildslave/unity/build/Editor/Mono/Prefabs/PrefabUtility.cs:1149)
UnityEditor.PrefabUtility.GetIconForGameObject (UnityEngine.GameObject gameObject) (at /Users/bokken/buildslave/unity/build/Editor/Mono/Prefabs/PrefabUtility.cs:1166)
UnityEditor.GameObjectInspector.DrawInspector () (at /Users/bokken/buildslave/unity/build/Editor/Mono/Inspector/GameObjectInspector.cs:256)
UnityEditor.GameObjectInspector.OnHeaderGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/Inspector/GameObjectInspector.cs:238)
UnityEditor.Editor.DrawHeader () (at /Users/bokken/buildslave/unity/build/Editor/Mono/Inspector/Editor.cs:683)
UnityEditor.PrefabOverridesTreeView+ComparisonViewPopup.DrawEditor (UnityEngine.Rect rect, UnityEditor.Editor editor, System.Boolean disabled) (at /Users/bokken/buildslave/unity/build/Editor/Mono/Prefabs/PrefabOverrides/PrefabOverridesTreeView.cs:735)
UnityEditor.PrefabOverridesTreeView+ComparisonViewPopup.OnGUI (UnityEngine.Rect rect) (at /Users/bokken/buildslave/unity/build/Editor/Mono/Prefabs/PrefabOverrides/PrefabOverridesTreeView.cs:659)
UnityEditor.PopupWindow.OnGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/PopupWindow.cs:90)
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <c8d0d7b9135640958bff528a1e374758>: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 <c8d0d7b9135640958bff528a1e374758>:0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <c8d0d7b9135640958bff528a1e374758>:0)
UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:342)
UnityEditor.HostView.Invoke (System.String methodName) (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:336)
UnityEditor.HostView.OldOnGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:129)
UnityEngine.Experimental.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:244)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr) (at /Users/bokken/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:179)

3. GUI Error: You are pushing more GUIClips than you are popping. Make sure they are balanced.
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr) (at /Users/bokken/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:179)