[MC-117564] Game crashes when you click "advancements" button while there is no advancement done

The bug

If you try to click the "advancements" button on the main menu while there is no advancement done, it will crash the game.

crash-2017-05-17_21.05.26-client.txt

Description: Updating screen events

java.lang.NullPointerException: Updating screen events
	at bly.b(SourceFile:61)
	at blh.a(SourceFile:350)
	at bhy.a(SourceFile:898)
	at bld.a(SourceFile:64)
	at blh.a(SourceFile:324)
	at blh.k(SourceFile:387)
	at blh.p(SourceFile:364)
	at bhy.t(SourceFile:1583)
	at bhy.ax(SourceFile:966)
	at bhy.a(SourceFile:406)
	at net.minecraft.client.main.Main.main(SourceFile:123)

Steps to reproduce

Create a new world
Pause the game and click the "advancements" button