The grass blocks in a roofed forest render as black if "Smooth lighting" is disabled

This is a regression of MCPE-186393

Steps to reproduce:

1. Find a roofed forest biome by typing the command /locate biome roofed_forest
2. Teleport to it.
3. Under Settings > Video turn off "Smooth lighting".

Observed results:
The top texture of the grass blocks within the roofed forest biome will render as black if you have smooth lighting disabled.

Expected results:
The top texture of grass blocks should render normally.