Sample Gradient when the result can be constant folded on the GPU is generating a failure:
```
Invalid VFX parent for sample Gradient : 2
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&)
```
```
Unity cannot compile the VisualEffectAsset at path "Assets/Repro_SampleGradient.vfx" because of the following exception:
System.ArgumentException: Invalid expression sheet
at (wrapper managed-to-native)
```

Step to repro:
- Import Repro_SampleGradient.package
- Open VisualEffect
- Switch from Runtime to Editor
- Observe the failure during compilation

!image-2022-11-29-14-17-22-883.png|thumbnail!

N.B.: This issue was related to 1284358