java.lang.NullPointerException: group

This happens when connecting to any server. When opening/creating a singleplayer world, the game crashes. This has happened for a month or two.

Game output when connecting to server: http://pastebin.com/GxtJiQyX
Game output when opening singleplayer world: http://pastebin.com/mMumEVW3
Crash report when opening singleplayer world: http://pastebin.com/wx959yGR