The Void biome generates terrain

Generating a single biome world with The Void biome instead generates terrain.

What I expected to happen was...:
An empty world would be generated

What actually happened was...:
Terrain was generated

Steps to Reproduce:
1. Create New World

2. World Type: Single Biome - The Void

3. Spawn in world, be greeted with a default landscape with no grass or mobs... spooky.