Multiplayer crash and realms doesn't work anymore

I start the launcher and I choose the snap 17w47a. Up to here there are no problems. I downloaded the version as soon as released and I created a world and I played it. Today, after three hours that I downloaded the snapshot, I wanted to try the multiplayer (now, I didn't want to play the multiplayer but I wanted to see if everything is ok and, if this don't happening , I knew that I had to write down the problem I had discovered). This is happened. I Entered in the main screen of minecraft and I clicked on Multiplayer. Immediately the game crashed with the error report. I tried again but the result was the same. I know I can't play on the snapshot but I want to report this bug. I hope this description is useful and I hope in an answer. 🙂

P.S. : I can't attach you a photo because I'm italian and the crash error is in italian too