How to reproduce:
1. Open the attached “IN-107935_minimal.zip” project
2. Open the “Worker BT” behavior graph
3. Right click in the behavior graph and select “Add…”
4. Add any node from the popup
5. Observe the behavior graph and the Console

Expected result: Node does not appear in the graph and “NullReferenceException” error is repeatedly thrown in the Console
Actual result: Node appears in the graph, no errors are thrown in the Console

Reproducible with: 1.0.10 (6000.0.54f1, 6000.1.12f1, 6000.2.0b10), 1.0.12 (6000.0.54f1, 6000.1.12f1, 6000.2.0b10)
Not reproducible with: 1.0.9 (6000.0.54f1, 6000.1.12f1, 6000.2.0b10)

Reproducible on: Windows 11
Not reproducible on: No other environments tested

Notes:
- An “NullReferenceException: Object reference not set to an instance of an object.” error is thrown in the Console
- The issue also reproduces when: removing a node, adding or removing a variable in the blackboard
- After reproducing the issue, further interactions with the behavior graph will not work (creating another node, adding variables to the blackboard, etc.)
- In 1.0.10 version all changes made to the graph are reflected, but the “NullReferenceException” error is thrown for each interaction with the graph