Witch Hut doesn't spawn witches

I have spawn proofed the area around and below the hut but withes wont spawn what so ever.

Other mobs spawn perfectly fine but witches won't.

Here is a world download the hut is at x30 z362

http://www.mediafire.com/file/fp17aisyvp465b4/Broken_Witch_Hut.mcworld/file

 

P.S. The world was generated in an android beta and then transferred to the PC.