fix: Group chats: Fix resetting settings to default
When using get_contact() on JIDs from the database, we might get a (new) BareContact back if we haven't seen this JID in our current session. This can be the case for group chats we've left in previous sessions. Call get_contact() with groupchat=True to make sure that we always get a GroupchatContact.
Fixes #11377 (closed)