I first log onto the snapshot and use the void preset and change the air layer to dirt

Put the summary of the bug you're having here

What I expected to happen was...:
Was a superflat world with a layer dirt and the void biome.

What actually happened was...:
Everything went well into I tried to go into the void which in turn crashed my game

Steps to Reproduce:
1. Go to create new world
2. Chose the new void preset and change the layer of air to dirt
3. Last when the world is loaded break the dirt layer and go into the void