Reproduction steps:
1) Open user's attached project
2) Open "DynaMusic" window ("Window > DynaMusic" or Ctrl+M)
3) Click on "New Music Controller.asset" button
4) Click on green "Entry" image
5) In left hand side menu click on "Add Transition" button
6) Create transition by clicking on any other image (for example red "End" image)
7) Try to undo with Ctrl+Z sixth step

Expected result:
Last action should delete last transition

Actual result:
Editor crashes

Stacktrace:
GUIView::UpdateScreenManager