In UE4 4.2.0. If a State is open as a tab, and you try to click it after you remove its parent State Machine, the editor crashes.
- Create Animation Blueprint
- Add a State Machine
- Add a new State inside State Machine
- Open State, so it exists as a tab in window
- Go to Animation Blueprint
- Delete State Machine
- Click on State tab
Suggestion of solution:
On deletion of state machine, check for any open tabs related to it and its children and close them.