[VFX Graph] NullReferenceException is thrown to the Console when switching from graph that was attached to target GO window to another graph

How to reproduce:
1. Open the attached package
2. Open 'VFX - 1' graph and attach it to the Target GO window
3. Open 'VFX - 2' graph

Expected result: No errors are thrown to the Console
Actual result: 'NullReferenceException: Object reference not set to an instance of an object' is thrown to the console

Reproduce with: 2022.1.0a1 (master)

Note:
- If the issue does not reproduce, press Set Capacity button in Debug section (attached gif of reproduction)