Repro steps:
1. Open the attached VFX
2. Try to delete them, disconnect them, or connect an output to them
3. Observe NullReferenceException (full exception below)

Note:
- Happened when the systems were using a custom output (Thomas' Distortion), but the effect was recompiled on a machine where the custom output files were missing. Re-adding the custom files later did not resolve the issue and these nodeblocks seem permanently corrupt.

NullReferenceException: Object reference not set to an instance of an object
UnityEditor.VFX.VFXContext.InnerSetData (UnityEditor.VFX.VFXData data, System.Boolean notify) (at Library/PackageCache/com.unity.visualeffectgraph@4.9.0-preview/Editor/Models/Contexts/VFXContext.cs:370)
UnityEditor.VFX.VFXContext.SetDefaultData (System.Boolean notify) (at Library/PackageCache/com.unity.visualeffectgraph@4.9.0-preview/Editor/Models/Contexts/VFXContext.cs:342)
UnityEditor.VFX.VFXContext.InnerUnlink (UnityEditor.VFX.VFXContext from, UnityEditor.VFX.VFXContext to, System.Int32 fromIndex, System.Int32 toIndex, System.Boolean notify) (at Library/PackageCache/com.unity.visualeffectgraph@4.9.0-preview/Editor/Models/Contexts/VFXContext.cs:311)
UnityEditor.VFX.VFXContext.UnlinkFrom (UnityEditor.VFX.VFXContext context, System.Int32 fromIndex, System.Int32 toIndex) (at Library/PackageCache/com.unity.visualeffectgraph@4.9.0-preview/Editor/Models/Contexts/VFXContext.cs:226)
UnityEditor.VFX.UI.VFXViewController.RemoveElement (UnityEditor.VFX.UI.Controller element) (at Library/PackageCache/com.unity.visualeffectgraph@4.9.0-preview/Editor/GraphView/Views/Controller/VFXViewController.cs:745)
UnityEditor.VFX.UI.VFXViewController.Remove (System.Collections.Generic.IEnumerable`1[T] removedControllers) (at Library/PackageCache/com.unity.visualeffectgraph@4.9.0-preview/Editor/GraphView/Views/Controller/VFXViewController.cs:642)
UnityEditor.VFX.UI.VFXView.Delete (System.String cmd, UnityEditor.Experimental.UIElements.GraphView.GraphView+AskUser askUser) (at Library/PackageCache/com.unity.visualeffectgraph@4.9.0-preview/Editor/GraphView/Views/VFXView.cs:410)
UnityEditor.Experimental.UIElements.GraphView.GraphView.DeleteSelectionOperation (System.String operationName, UnityEditor.Experimental.UIElements.GraphView.GraphView+AskUser askUser) (at C:/buildslave/unity/build/Modules/GraphViewEditor/Views/GraphView.cs:1132)
UnityEditor.Experimental.UIElements.GraphView.GraphView.DeleteSelectionCallback (UnityEditor.Experimental.UIElements.GraphView.GraphView+AskUser askUser) (at C:/buildslave/unity/build/Modules/GraphViewEditor/Views/GraphView.cs:1061)
UnityEditor.Experimental.UIElements.GraphView.GraphView.<BuildContextualMenu>m__9 (UnityEngine.Experimental.UIElements.DropdownMenu+MenuAction a) (at C:/buildslave/unity/build/Modules/GraphViewEditor/Views/GraphView.cs:690)
UnityEngine.Experimental.UIElements.DropdownMenu+MenuAction.Execute () (at C:/buildslave/unity/build/Modules/UIElements/DropdownMenu.cs:99)
UnityEditor.Experimental.UIElements.EditorMenuExtensions+<PrepareMenu>c__AnonStorey0.<>m__0 () (at C:/buildslave/unity/build/Editor/Mono/UIElements/EditorMenuExtensions.cs:33)
UnityEditor.GenericMenu.CatchMenu (System.Object userData, System.String[] options, System.Int32 selected) (at C:/buildslave/unity/build/Editor/Mono/GUI/GenericMenu.cs:121)