quick_frontend, primitivus: various fixes (MUC and cached signals):

- actually call the cached signals, everything was there but the call was not done
    - display '[]' instead of '[None]' when group message coming from the room (no resource)
    - catch the exception when trying to delete an occupant who's not in the room
    - do not cache a "main resource" for MUC entities

frontends/src/primitivus/chat.py

@@ -73,7 +73,7 @@ class ChatText(urwid.FlowWidget):
             if self.parent.show_short_nick:
                 render_txt.append(('my_nick' if self.my_mess else 'other_nick', "**" if self.my_mess else "*"))
             else:
-                render_txt.append(('my_nick' if self.my_mess else 'other_nick', "[%s] " % self.nick))
+                render_txt.append(('my_nick' if self.my_mess else 'other_nick', "[%s] " % (self.nick or '')))
         render_txt.append(self.message)
         txt_widget = urwid.Text(render_txt, align=self.align)
         if self.is_info:
@@ -188,7 +188,10 @@ class Chat(PrimitivusWidget, QuickChat):
             nick = entity.resource
             show = contact_list.getCache(entity, C.PRESENCE_SHOW)
             if show == C.PRESENCE_UNAVAILABLE or show is None:
-                self.occupants_list.deleteValue(nick)
+                try:
+                    self.occupants_list.deleteValue(nick)
+                except ValueError:
+                    pass
             else:
                 values = self.occupants_list.getAllValues()
                 markup = self._buildOccupantMarkup(entity)