[MC-124206] Opening language selection crashes if resource pack specifying non-existent language is loaded

The bug

When you try to open the language selection while having a resource pack, which specifies a non-existing language in the pack.mcmeta file, loaded the game crashes.

18w02a: crash-2018-01-12_18.07.35-client.txt

Description: Rendering screen

java.lang.NullPointerException: Rendering screen
	at brk$a.a(SourceFile:114)
	at bpt.a(SourceFile:371)
	at bpt.a(SourceFile:194)
	at brk.a(SourceFile:67)
	at cau.a(SourceFile:990)
	at bob.b(SourceFile:822)
	at bob.a(SourceFile:382)
	at net.minecraft.client.main.Main.main(SourceFile:140)

How to reproduce

Download the attached file MC-124206 resource pack.zip and place it in the resourcepacks folder
Load the resource pack
Try opening the language selection