Leaf Litter replaces leaves in world gen

When generating a new world, the leaf litter can replace leaves when the leaves touches the ground.

Steps to Reproduce

1. Go create a new world using seed and coordinates below.
   1431655327083997756
   -1657 72 -2151
2. Look at the trees.

Expected Result
The tree should stay intact with the proper leaves.

Observed Result
The leaf litter replaces some of the leaves upon world gen.