Crash when attempting to add task to just deleted list

[TheLastProject]

How to reproduce:

1. Create new list
2. Switch to list
3. Delete list
4. Close sidebar so you stay on the just deleted list
5. Press add task floating action button
6. Mirakel crashes

There are several solutions available. To me, the sanest seems to be to not allow the sidebar to be closed after deleting the active list so that the user is forced to choose another list.

This issue is probably low priority, as there is no damage or data loss and the crash can be trivially avoided, but I still felt like reporting it.