Crash when loading specific world

Put the summary of the bug you're having here

What I expected to happen was...:
World will load

What actually happened was...:
Minecraft crashes

15w41b

Description: Exception ticking world

java.lang.ClassCastException: air cannot be cast to ajv
	at avo$c.a(SourceFile:1716)
	at avl.a(SourceFile:42)
	at avh.a(SourceFile:94)
	at asm.b(SourceFile:165)
	at arj.a(SourceFile:802)
	at arj.a(SourceFile:784)
	at ln.d(SourceFile:115)
	at lt.a(SourceFile:85)
	at lu.c(SourceFile:143)
	at lo.d(SourceFile:207)
	at net.minecraft.server.MinecraftServer.D(SourceFile:610)
	at net.minecraft.server.MinecraftServer.C(SourceFile:546)
	at bvw.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:450)
	at java.lang.Thread.run(Unknown Source)

15w45a

Description: Exception ticking world

java.lang.ClassCastException: ajc cannot be cast to akg
	at awc$c.a(SourceFile:1691)
	at avz.a(SourceFile:42)
	at avv.a(SourceFile:94)
	at ata.b(SourceFile:165)
	at arw.a(SourceFile:802)
	at arw.a(SourceFile:784)
	at lp.d(SourceFile:115)
	at lv.a(SourceFile:85)
	at lw.c(SourceFile:146)
	at lq.d(SourceFile:221)
	at net.minecraft.server.MinecraftServer.D(SourceFile:610)
	at net.minecraft.server.MinecraftServer.C(SourceFile:546)
	at bxx.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:450)
	at java.lang.Thread.run(Thread.java:745)

Steps to Reproduce:
1. It happens only in this world: http://ulozto.cz/xGaq87V5/snapshot-tests-zip
2. minecraft crashes
3. ...