Exploit with spawners and withers

Found in creative, maybe possible in survival. A blue wither skull drops a spawner if it hits one every once in a while. Here's a pic of a dropped spawner after placing a few. http://imgur.com/5BVeq I have the Spawner GUI mod, but my logic narrowed it down that the mod would have no effect on whatever happens to them, besides a right click. Perhaps someone could try without the mod first, just to be sure? I really want to make sure its not just the mod, because this could throw off a lot of balance if people were to use it like the sand duper, because food is one of minecraft's biggest and most important resources.