Editor undo sometimes causes transition to be deleted in code, but not in the visualiser

[Johannes]

bug.mov

As illustrated in the video, the following steps reproduce the issue.

1. turn a transition into a guarded transition through the editor
2. immediately undo the action

The entire original transition will be deleted from the code, but will remain in the visualiser.

[David Khourshid]

Thanks for the report; investigating.