Reproduction steps:
1. Open attached project
2. Delete any transition form "Any State"
3. In console "NullReferenceException: Object reference not set to an instance of an object" error will appear. Also, the transition from "Entry" will be deleted too. (check Repro.gif)

Actual result: NullReferenceException error will appear and the transition from "Entry" will be deleted.

Expected result: NullReferenceException error should not appear and the transition from "Entry" should't be deleted.

Notes:
- Doesn't reproduce on a new project.
- Reproduces only when the project is opened for the first time.
- After deleting the transition and then pressing Ctrl+Z another NullReferenceException error will appear.

Regression introduced in: 5.2