Light levels in the F3 debug menu aren't accurate when standing on soul sand

The Bug:

Light levels in the F3 debug menu aren't accurate when standing on soul sand.

Steps to Reproduce:

1. Enable the F3 debug menu and place down some soul sand.
2. Stand on top of the soul sand and pay close attention to what the game states your light levels are.
3. Take note as to whether or not light levels in the F3 debug menu aren't accurate when standing on soul sand.

Observed Behavior:

Light levels always appear as "0" when standing on soul sand.

Expected Behavior:

Light levels would be accurate when standing on soul sand.