How to reproduce:
1. Create and open a new project
2. Drag the cursor into the Scene window
3. Press Shift + Space
4. Right-click on the Scene window and drag the mouse where another window will be after minimizing
5. Press Shift + Space

Expected result: scene view does not freeze when minimized
Actual result: scene view freezes when minimized

Reproducible with: 2018.3.0a6, 2018.4.11f1, 2019.2.10f1, 2019.3.0b7, 2020.1.0a9
Not reproducible with: 2017.4.33f1, 2018.3.0a5

Workarounds to unfreeze the Scene window:
- Clicking on the scene gizmo (colored x, y, z arrows in the upper right corner of the Scene window)
- Right-clicking on the Scene tab and selecting UIElements Debugger