I created a villager with the following NBT tag:
http://pastebin.com/W9X6aGkG
When I traded a stack of Emeralds (in return for 4 stacks of raw oak wood), he did his usual "Hmm" overlaying many times (-> 16 times, I guess, because of 16 items traded 16 times = 4 stacks). I wanted to click through to see if he generated any new offer, so I clicked fast (like 5 clicks/second or so) to the end, and while the screen showed the birch wood, the game crashed with the exception below.

Hope this was detailed enough. Didn't find any similar issues while searching.