On creating "Category" Node under New Visual Graph throwing ArgumentNullException, refer attached video and Stack Trace

Steps to repro:
1. Create a new project
2. Windows > Package Manager > Visual Effects Graph > Install
3. Windows > Effects > Visual effect Graph > Create VFX Graph.
4. New Graph > (+) Button > Category.

Actual Result:
ArgumentNullException is thrown on creating a Category node from New Visual Graph.

Expected Result:
"Category" Node gets created without any exception thrown in the Console

Reproducible in:
2020.2.0a8, 2020.1.0b6 with Package Version preview.13 - 9.0.0, 8.0.1

working fine in:
2020.2.0a8, 2020.1.0b6 with Package Version 7.3.1

NOTE:
Visual Effect Graph is introduced in 2019.3.0a10.

Environment:
Only macOS 10.15

Stack Trace:
ArgumentNullException: Value cannot be null.
Parameter name: source
System.Linq.Enumerable.Any[TSource] (System.Collections.Generic.IEnumerable`1[T] source, System.Func`2[T,TResult] predicate) (at <351e49e2a5bf4fd6beabb458ce2255f3>:0)
UnityEditor.VFX.UI.VFXBlackboard.OnAddCategory () (at Library/PackageCache/com.unity.visualeffectgraph@8.0.1/Editor/GraphView/Blackboard/VFXBlackboard.cs:406)
UnityEditor.GenericMenu.CatchMenu (System.Object userData, System.String[] options, System.Int32 selected) (at /Users/builduser/buildslave/unity/build/Editor/Mono/GUI/GenericMenu.cs:121)