The "sell" tag from The "Offers" tag from summoning a Villager does not work making it crash the game

Well this is embarrassing I was trying to summon a Villager with a custom trade but there was nothing in the sell slot. Making the game crash.

"---Minecraft Crash Report--
//Uh... Did I do that

Time: 8/28/14 10:19 AM

java.lang.NullPointerExeption: Updating screen events"