if ( a.height == 0 && a.walkable )
if ( a.height == 0 && a.walkable && !b.walkable )
	bool operator()( stBlockItem a, stBlockItem b )	{		// If the items have the same top, the one with the surface flag has precedence		int itemTopA = a.height + a.z;		int itemTopB = b.height + b.z;		if ( itemTopA == itemTopB )		{			if ( a.height == 0 && a.walkable )			{				return true;			}			if ( b.height == 0 && b.walkable )			{				return false;			}		}		return ( itemTopA > itemTopB );	}