[17w49b] Loading 1.12 structure blocks crashes and corrupts world.

I ran this command in a repeating command block:

/execute if block -22 65 133 minecraft:oak_button[facing=east,powered=true]

and had a comparator running out to a, pre-existing in 1.12, structure block.

When I pushed said button the game crashed and I can no longer see the world in the list of singleplayer maps.

My guess is 1.12 and below structure block files have to be moved to a new folder or resaved before use in 1.13+.

Edit: I've added what I think was the first crash don't know why it's a server.txt when this was a singleplayer world. I did import it from my server if that means anything. But I was playing it locally to test out learning how to replace the testfor commands.