How to reproduce:
1. Create a new project
2. Go to the menu bar "Edit > Project Settings..."
3. In the "Project Settings" window go to "Player > Other Settings" and disable "Auto Graphics API for Linux"
4. In the "Graphics APIs for Linux" section select and remove "OpenGL Core"
5. Restart the Editor when prompted
6. In the same "Project Settings" window go to "Player > Other Settings" and under "Rendering" set the "Color Space" to "Linear"

Expected result: the color space switches to "Linear"
Actual result: the Editor freezes

Reproducible with: 2019.4.7f1, 2019.4.8f1
Not reproducible with: 2018.4.26f1, 2019.4.6f1, 2019.4.9f1, 2020.1.3f1

Note: Reproducible on Ubuntu 18.04, not reproducible on Windows 10