Crash when deleting element with command-line tool on the palette and clicking on it on the scene

Scenario:

1. Add a custom element with command-line tool to the scene.
2. Delete it on the elements palette.
   Current result: the added element is still on the scene.
   Expected result: the added element should also be deleted.
3. Click on the added element on the scene.
   Current result: UGENE crashes.