Bug/crash in minecraft v1.7.5

i tried starting a new world with minecraft v1.7.5

What I expected to happen was...:
i thought a new Biome would pop up but i guess not, i also noticed that i haven't yet got some of the new Biomes.

What actually happened was...:
my minecraft crashed.

Steps to Reproduce:
1. Start minecraft for 1.7.5
2. do large biomes
3. and create new world until it crashes, i guess?