*Steps to reproduce:*

1. Import the attached VFX

2. Open it

3. Convert one of the Multiply Color Over Life to Subgraph block

4. Open New_VFX_Subgraphblock and switch to New VFX graph instead

5. Delete New_VFXSubgraphblock

7. Create remaining Color Over Life to Subgraph block (with the same name as previous one)

*Actual results:* Error is thrown 

*Expected results:* No errors are thrown 

*Reproducible with versions:* 6000.1.0b2, 6000.0.33f1

*Not reproducible with versions:* 

*Can't test with versions:* 

*Tested on (OS):* Windows

*Notes:*

I did not test 22.3 version 

Error message: NullReferenceException: VFXMemorySerializer::StoreObject failure.
UnityEditor.VFX.VFXMemorySerializer.StoreObjectsToByteArray (UnityEngine.ScriptableObject[] objects, UnityEngine.CompressionLevel compressionLevel) (at <2d63d1f8f515462a9b671d97c227cbe3>:0)
UnityEditor.VFX.VFXGraph.Backup () (at C:/Users/vitaskruibyte/Documents/unity/packages/com.unity.visualeffectgraph/Editor/Models/VFXGraph.cs:829)

During reproduction is possible to bump into another bug when subgraph created for the second time cannot be opened [UUM-85270|https://jira.unity3d.com/browse/UUM-85270]. You can bypass this issue by closing and reopening an Editor

Error message: Exception thrown while invoking [OnOpenAssetAttribute] method 'VisualEffectAssetEditor:OnOpenVFX (int,int)' : NullReferenceException: Object reference not set to an instance of an object
UnityEditor.VFX.UI.VFXViewWindow+<>c_{_}DisplayClass9_0.<GetWindow>b{_}_0 (UnityEditor.VFX.UI.VFXViewWindow x) (at C:/Users/vitaskruibyte/Documents/unity/packages/com.unity.visualeffectgraph/Editor/GraphView/VFXViewWindow.cs:80)