fix: Fix measure messages.

This just counts messages and should not block processing messages. Breaks visitor messages coming from s2s and no session params are available.

resources/prosody-plugins/mod_measure_message_count.lua

 
     local session = event.origin;
     if not session or not session.jitsi_web_query_room then
-        return false;
+        return;
     end
 
     -- get room name with tenant and find room.
     if not room then
         module:log('warn', 'No room found found for %s/%s',
             session.jitsi_web_query_prefix, session.jitsi_web_query_room);
-        return false;
+        return;
     end
 
     if not room._muc_messages_count then