Crash when deleted symbol inserted

To reproduce:
1. Open up the symbols dialog
2. Click on a symbol, and hit "Delete"
3. Click on a note in the score
4. Double click on the now empty square from where the symbol was deleted

Is there a reason the "Delete" button exists? There doesn't seem to be a way to add a new symbol in place of the deleted one.

I'm running GNU/Linux and 0.9.6 2148