Progress modal window stays on top of every other window and cannot be moved

Reproduction steps:
1. Create a new 3D project
2. Try moving the progress modal window or switching to another window

Expected result: The modal window can be moved and is hidden when switching to another window
Actual result: The modal stays put when trying to move it and is not hidden when switching to another window

Reproducible with: 2022.3.10f1, 2023.1.15f1, 2023.2.0b4, 2023.2.0b11, 2023.3.0a1, 2023.3.0a7
Not reproducible with: 2021.3.30f1, 2023.2.0b3

Reproducible on: Ubuntu 23.04
Not reproducible on: no other environment tested

Notes:

• If there is no progress modal window when creating a project (2023), try building that same project and the progress modal will show up

• Issue introduced by [Internal link] fixes