gc: last selected contact can be in a closed room, so prevent KeyError tb

src/groupchat_window.py

@@ -1339,6 +1339,8 @@ current room topic.') % command, room_jid)
 		if self._last_selected_contact is not None:
 			# update unselected row
 			room_jid, nick = self._last_selected_contact
+			# last selected can be in a closed room, so prevent KeyError
+			if room_jid in self.list_treeview.keys():
 				self.draw_contact(room_jid, nick)
 		if selected_iter is None:
 			self._last_selected_contact = None