I was testing out the latest snapshot when all the sudden I got a strange crash I've never seen before. When I tried to rejoin, I crashed again. The world is no longer accessible. Don't worry, the world itself wasn't important. Regardless, it happened when I had opened a chest in a trial chamber. I had already opened that chest, and I was just opening it again to retrieve some loot I'd left there. I was using a firework crossbow to kill the mobs there.