Nether Crash with Signs?

I was playing on a LAN outted minecraft map that was originally made in 1.8. We updated to the snapshot, and I was messing around in the Nether to build a house, in creative. I go to place a sign on Polished Granite, next to a Nether Portal, and the game crashes. My roommate managed to delete my player data, which allowed me to get back in, but I couldn't get back in at all otherwise. I'll be attaching a screenshot of the error it kept giving me.