On clicking Color Picker in "HDR Gradient Editor", "HDR Color" and "HDR Gradient Editor" Windows close after opening for a sec. Refer attached video.

Steps to reproduce:
1) Open the attached project.(UIElementsTestSuite-master)
2) UIE Test Suite > Open FTP
3) Menu Bar > UI Test Suite > Open FTP > Controls > Open Window
4) Gradient Editor > Color Picker

Actual Result:
Color Picker and HDR Gradient Editor Window closes

Expected Result:
Color Picker window opens

Reproducible in: 2020.1.0a11,2020.1.0a10,

Working fine on: 2020.1.0a9, 2019.3.0b9

Environment: Occurs only on Linux (ubuntu 18.04.3 LTS)