Core/Groups: do not allow lfg groups to change the loot method

src/server/game/Handlers/GroupHandler.cpp

@@ -669,6 +669,9 @@ void WorldSession::HandleLootMethodOpcode(WorldPacket& recvData)
     if (!group->IsLeader(GetPlayer()->GetGUID()))
         return;
 
+    if (group->isLFGGroup())
+        return;
+
     if (lootMethod > NEED_BEFORE_GREED)
         return;