On certain servers which give/take away a shield to imitate blocking with a sword on 1.8, Forge 1.9 crashes. I tested this using Forge build 1877 with no mods on the hypixel.net server. To reproduce, join a game (in 1.9) which uses swords (I tested using SkyWars) and right click with a sword in your hand. It may take a couple right clicks to crash the game.
fml-client-latest: http://pastebin.com/pmVEvSb1
Edit: Tested again with the new recommended build that came out today, still crashes with the same message.
