Perhaps now you begin to see that any inventory editor will have the risk of allowing you to add debug items that are not meant for gameplay.
That's like complaining that using a debug cheat code crashes your game. Simple answer is: Don't use it, then.
Kinda beyond the point. There's nothing that should be left over that's accessible by any "simple" means that should crash MC, but I shan't argue with you. I was just bringing the crash to Zip's attention really.