Crash when generating chunks containing Strongholds

World was created in 14w26c, then loaded into 14w27b. When moving to un-generated chunks that contain one of the 3 world strongholds, the game crashes. Reloading the game will continue to crash in the area until the stronghold has been completely generated.

After reloading, and once crashing has ceased, the generated stronghold will appear to contain doors (both wooden and iron) that aren't really there. Pressing the button on a wall or placing a torch in front of the doors will result in the door disappearing.

Description: Exception while updating neighbours
java.lang.IllegalArgumentException: Cannot get property azh{name=half, clazz=class aqo, values=[upper, lower]} as it does not exist!
	at ayx.b(SourceFile:120)
	at aqn.a(SourceFile:156)
	at aqn.a(SourceFile:163)
	at amp.e(SourceFile:470)
	at amp.d(SourceFile:434)
	at amp.c(SourceFile:405)
...
-- Block being updated --
Details:
	Source block type: ID #0 (tile.air // aon)
	Block: minecraft:iron_door[facing=east,half=upper,hinge=left,open=false,powered=true]