check sender

Author: Half-Shot

mautrix_telegram/portal/telegram.py

@@ -707,8 +707,8 @@ async def handle_telegram_message(self, source: 'AbstractUser', sender: p.Puppet
                            "the likely duplicate message now.")
             await intent.redact(self.mxid, event_id)
             return
-
-        UserActivity.update_for_puppet(sender, evt.date)
+        if sender is not None:
+            UserActivity.update_for_puppet(sender, evt.date)
         self.log.debug("Handled telegram message %d -> %s", evt.id, event_id)
         try:
             DBMessage(tgid=TelegramID(evt.id), mx_room=self.mxid, mxid=event_id,