How to reproduce:
1. Open the "Render slice index test" Scene in the attached "1198097.zip" Unity project
2. Build and run the Scene
3. Observe the Scene in the Player

Expected results: the two squares in the Scene become red and green
Actual results: the squares remain gray

Reproducible with: 2019.2.16f1, 2019.3.0f2, 2020.1.0a16
Could not test with: 2017.4.35f1, 2018.4.14f1

Notes:
1. Not reproducible in Play Mode in the Editor
2. Reproducible in Mac OS X and Windows standalone builds, iOS, Android builds
3. Could not test on 2017.4 and 2018.4 due to inability to use null propagating operator

Devices reproducible with:
- iPad Pro 12.9" (2018) (iOS 13.1.2)