Fix mention-related KeyError in message callback

TODO.md

@@ -1,7 +1,7 @@
 # TODO
 
+- mention color in local echo
 - cpu usage
-- room.mentions += 1 key error before registration
 
 ## Main goals for next version
 

src/backend/nio_callbacks.py

@@ -101,16 +101,17 @@ class NioCallbacks:
             room_id = room.room_id,
         )
 
-        if HTML_PROCESSOR.user_id_link_in_html(co, self.client.user_id):
-            rooms = self.client.models[self.client.user_id, "rooms"]
-            rooms[room.room_id].mentions += 1
-
         mention_list = HTML_PROCESSOR.mentions_in_html(co)
 
         await self.client.register_nio_event(
             room, ev, content=co, mentions=mention_list,
         )
 
+        if HTML_PROCESSOR.user_id_link_in_html(co, self.client.user_id):
+            rooms = self.client.models[self.client.user_id, "rooms"]
+            rooms[room.room_id].mentions += 1
+
+
 
     async def onRoomMessageNotice(self, room, ev) -> None:
         await self.onRoomMessageText(room, ev)