Exit game --> console spams with "Error executing task"

My second bug report for the day.

(Console report is below)

[10:41:20] [Client thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:222) ~[?:1.6.0_65]
at java.util.concurrent.FutureTask.get(FutureTask.java:83) ~[?:1.6.0_65]
at g.a(SourceFile:46) [15w43b.jar:?]
at bbp.as(SourceFile:932) [15w43b.jar:?]
at bbp.a(SourceFile:384) [15w43b.jar:?]
at net.minecraft.client.main.Main.main(SourceFile:125) [15w43b.jar:?]
Caused by: java.lang.NullPointerException
at bjw.a(SourceFile:593) ~[15w43b.jar:?]
at fz.a(SourceFile:53) ~[15w43b.jar:?]
at fz.a(SourceFile:13) ~[15w43b.jar:?]
at fh$1.run(SourceFile:13) ~[15w43b.jar:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:439) ~[?:1.6.0_65]
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) ~[?:1.6.0_65]
at java.util.concurrent.FutureTask.run(FutureTask.java:138) ~[?:1.6.0_65]
at g.a(SourceFile:45) ~[15w43b.jar:?]
... 3 more