a random chunck lake pit appeared

a random chunck lake pit appeared (it sort of looks like the old void in 1.8 beta multiplayer exept less deep and less buggy also before you say i should have loaded it in 1.6.4 not only were plugins O.O.D but the world did not seem to be needed to be deeply explored, areas pre-spawned are fine it is the new areas that messed up)

What I expected to happen was that the world on my server would load smoothly

What actually happened was this random chunck lake pit in the ground appeared at the edge of a mega taiga biome

Steps to Reproduce th bug
1. load a world on 1.6.2. and then convert over to 1.7.
2. find a mega taiga biome and look around,
3. soon you might be able to find the same result or something close to it