Game crashes when connecting to a server

When connecting to my server, my game just crashes.
Log says:

Unreported exception thrown!
java.lang.NullPointerException
at vn$a.a(SourceFile:77)
at vn$a.a(SourceFile:63)
at axq.a(SourceFile:210)
at bfs.a(SourceFile:263)
at abd.a(SourceFile:1105)
at ckd.b(SourceFile:1183)
at ckd.a(SourceFile:1083)
at ckd.a(SourceFile:944)
at bxe.b(SourceFile:820)
at bxe.a(SourceFile:381)
at net.minecraft.client.main.Main.main(SourceFile:141)