Add some ASSERT in add/remove obj to/from grid.

src/server/game/Maps/Map.cpp

@@ -255,6 +255,7 @@ void Map::AddToGrid(Creature* obj, Cell const& cell)
     obj->SetCurrentCell(cell);
 }
 
+//TODO: cell is not needed. Just an unlink is enough.
 template<class T>
 void Map::RemoveFromGrid(T* obj, Cell const& cell)
 {
@@ -287,12 +288,12 @@ void Map::SwitchGridContainers(T* obj, bool on)
 
     if (on)
     {
-        grid.RemoveGridObject<T>(obj);
+        grid.RemoveGridObject<T>(obj); //not really necessary if there were no ASSERT in remove/add
         grid.AddWorldObject<T>(obj);
     }
     else
     {
-        grid.RemoveWorldObject<T>(obj);
+        grid.RemoveWorldObject<T>(obj); //not really necessary if there were no ASSERT in remove/add
         grid.AddGridObject<T>(obj);
     }
     obj->m_isWorldObject = on;