[MC-92230] 15w45a - first time to the end, generated the landing platform then crashed

I have been playing on 1.9 snapshots in a new world and just got to the end portal. I went through the end portal and it loaded the landing area in the end (obsidian floor and end stone walls) then the game crashed. I could see that the ender dragon had loaded in as the health bar appeared in the top of the screen. Once I moved around on the platform it crashed the game and went back to the launcher (version 1.6.48)

Description: Exception generating new chunk

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429)
	at java.util.HashMap$KeyIterator.next(HashMap.java:1453)
	at ny.<init>(SourceFile:26)
	at arw.<init>(SourceFile:82)
	at arw.<init>(SourceFile:89)
	at atg.a(SourceFile:176)
	at lp.d(SourceFile:99)
	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)