Debug world crashing in the nether.

What I expected to happen was...:
A playable nether world in the debug world type.

What actually happened was...:
Game crashing when loading level after a restart.

Steps to Reproduce:
1. Create a new world with the Debug type selected.
2. Find any of the nether portal blocks while in creative mode.
3. Enter the nether and wait for it to load.
4. Close out of the game and attempt to enter the world you created.

The game should crash at this point for some reason. I've attached the world I am experiencing the issue with, hopefully that helps.