Blue, Red and Yellow color patches are missing in PBR Validation Settings for all the three sections.

Steps to repro:
1. Create a new project.
2. Create a new Scene.
3. Scene > Shaded Mode > Material Validation > Validate Albedo.

Actual Result:
Color patches are missing in PBR Validation Settings Preview window

Expected Result:
Blue, Red & Yellow patches are there in PBR Validation Settings Preview window

Reproducible in:
2020.2.0a13, 2020.1.0b11, 2019.3.15f1, 2019.3.0b5.

Working Fine in:
2019.2.0f1.

Note: Could not test the previous version from 2019.3.0b5 to 2109.3.0a1, due to Editor crashes.

Environment:
Occurring on Windows 10 & Mac 10.15.