Nested filters causes rendering issues

Steps to reproduce:

1. Open the Bagel game project: https://github.com/Unity-Technologies/BagelGame
2. Open MainMenuScreen.uxml in the builder
3. Select the #main-menu-screen element
4. Add a DropShadow filter

Actual results: The filter makes everything black (see attached screenshot)

Expected results: The filter should add a drop-shadow

Reproducible with versions: 6000.6 6000.5

Not reproducible with versions: 

Can’t test with versions: 

Tested on (OS): 

Notes:

•