Bastion Remnants generation

Hi,

On this beta I cannot locate any magma cube mob spawners in bastions.

What should happen:
In the treasure room, a magma cube spawner block will generate relatively near to the loot.

What happens:
No mob spawner generated

Steps to Reproduce:

1. Create a world using the seed -564456128
2. /tp @s 684 38 546 in the nether