Fixed
- Deleting the last topic of a child board results in a `NoReverseMatch` error on
the index page (Thanks ErikKalkoken)
Changed
- Refactoring of logic for updating the first and last message on board and topic
(Thanks ErikKalkoken)
- Demoted `Board.update_last_message()` and `Topic.update_last_message()` to private
methods. Those should no longer be called from outside the module, because they're called implicitly by `save()` and `delete()` when needed. Except for bulk
methods, where e.g. `save()` is not called automatically. Test now also no longer
test this method directly. (Thanks ErikKalkoken)