Applied this change and "Edit Menu Item" overlay dialog correctly shows "You must choose a project" resp. "You must choose a room." error message, now without an exception.
Go to /home/menu/configure/custom/ and also to /home/menu/configure/global/ and try:
- Add Label with name `0` / `1` / `1.123` etc.
- Add Label, Save again
- Add Link, Save again
- Add Application, Save again
- Add Divider, Save again
- Add Conpherence, Save again
- Add Link, Save Again
- Add Motivator (Cat Facts), Save again
- Add Form, Save again
- Order Items
- Activate/Disable Built-in Home (unrelated)
- Remove all the above
Also, tried on a Project menu.