Converting empty groups along with nodes into a subgraph prevents subgraph creation and throws errors

Steps to reproduce:

1. Open VFX Graph
2. Add Group node
3. Add any node to the workspace e.g. Get Age (make sure it is not in group)
4. Right click select Get Age and select Convert To Subgraph Operator

Actual results: Subgraph is not created and error is thrown

Expected results: Subgraph is created (at least it allows to create subgraphs when nodes are in groups)

Reproducible with versions: 6000.0.33f1, 6000.2.0a4

Not reproducible with versions: n/a

Can’t test with versions: n/a

Tested on (OS): Windows

Notes:

NullReferenceException: Object reference not set to an instance of an object
UnityEditor.VFX.UI.VFXPaste.PasteGroupNodes (UnityEditor.VFX.UI.VFXCopyPasteCommon+SerializableGraph serializableGraph, UnityEngine.Vector2 center, UnityEditor.VFX.VFXUI ui) (at ./Library/PackageCache/com.unity.visualeffectgraph/Editor/GraphView/Views/VFXPaste.cs:619)
UnityEditor.VFX.UI.VFXPaste.PasteAll (UnityEditor.VFX.UI.VFXViewController viewController, UnityEngine.Vector2 center, UnityEditor.VFX.UI.VFXCopyPasteCommon+SerializableGraph& serializableGraph, UnityEditor.VFX.UI.VFXView view, UnityEditor.VFX.UI.VFXGroupNodeController groupNode, System.Collections.Generic.List`1[T] nodesInTheSameOrder) (at ./Library/PackageCache/com.unity.visualeffectgraph/Editor/GraphView/Views/VFXPaste.cs:287)
UnityEditor.VFX.UI.VFXPaste.DoPaste (UnityEditor.VFX.UI.VFXViewController viewController, UnityEngine.Vector2 center, System.Object data, UnityEditor.VFX.UI.VFXView view, UnityEditor.VFX.UI.VFXGroupNodeController groupNode, System.Collections.Generic.List`1[T] nodesInTheSameOrder) (at ./Library/PackageCache/com.unity.visualeffectgraph/Editor/GraphView/Views/VFXPaste.cs:140)