Top texture of blocks become blurry in the inventory when the GUI scale is set to -1

Summary:
When the GUI scale is switched from 0 to -1, all the top textures of blocks in the inventory become blurry. 

Steps to Reproduce:

1. Place some blocks in your inventory
2. Set the GUI scale to -1
3. Look at the top texture of the blocks

Observed Results:
The top textures are blurry.

Expected Results:
The top textures remain clear and look the same as they do when the GUI scale is set to 0.