Properly disconnect add person connection.

[BentleyJOakes]

When disconnecting, properly unhook the connection changed in previous commit.

Should fix #833

[TheJackiMonster]

I think line 955 should also be added in this hacky try & catch block... ^^'
self.btnAddPerso.clicked.connect(self.lstCharacters.addCharacter, F.AUC)

Actually seeing this code makes me want to address it properly but it should be fine then.