Model error : wrong parent errors are thrown on opening VFX Subgraph Block.

Steps to repro:
1. Create a new HDRP template project.
2. Project Window > Click "+" > Visual Effects > Visual Effect Subgraph Block.
3. Open Subgraph Block > Select Block Subgraph node > Reset.
4. Close Subgraph Block & Open again.

Actual Result:
Model error : wrong parent errors are thrown in the console.

Expected Result:
No error in the console.

Reproducible in:
2020.2.0a13, 2020.1.0b11, 2020.1.0a23 with Package version 9.0.0, 8.1.0.

Environment:
Occurring on Windows 10 & Mac 10.15.

Stacktrace:
Model error : wrong parent. expected:''(VFXGraph) actual:null(VFXModel)
UnityEditor.VFX.UI.VFXViewWindow:LoadResource (UnityEditor.VFX.VisualEffectResource,UnityEngine.VFX.VisualEffect)
VisualEffectAssetEditor:OnOpenVFX (int,int) (at library/packagecache/com.unity.visualeffectgraph@9.0.0-preview.13/editor/inspector/vfxasseteditor.cs:113)
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&)

Model error : 'Block Subgraph'(VFXBlockSubgraphContext) wrong graph. expected:''(VFXGraph) actual:null(VFXModel)
UnityEditor.VFX.UI.VFXViewWindow:LoadResource (UnityEditor.VFX.VisualEffectResource,UnityEngine.VFX.VisualEffect)
VisualEffectAssetEditor:OnOpenVFX (int,int) (at library/packagecache/com.unity.visualeffectgraph@9.0.0-preview.13/editor/inspector/vfxasseteditor.cs:113)
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&)Model error : 'Block Subgraph'(VFXBlockSubgraphContext) wrong graph. expected:''(VFXGraph) actual:null(VFXModel)
UnityEditor.VFX.UI.VFXViewWindow:LoadResource (UnityEditor.VFX.VisualEffectResource,UnityEngine.VFX.VisualEffect)
VisualEffectAssetEditor:OnOpenVFX (int,int) (at library/packagecache/com.unity.visualeffectgraph@9.0.0-preview.13/editor/inspector/vfxasseteditor.cs:113)
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&)