How to reproduce:
1. Create a new project and open it
2. Create a new material and inspect it
3. In the material preview's top right, there are 5 different buttons. Two of the rightmost ones are right-clickable, try to right-click the reflection probe button
4. The Preview should undock, right-click it again to dock it
5. Keep repeating the steps 3 and 4 until the Editor crashes (Crashes in like 3-5 tries for me)

Expected result: The buttons do not undock the preview on right-click and the Editor does not crash when docking/undocking the preview window
Actual result: The buttons undock the window on right-click and the Editor occasionally crashes when docking/undocking the preview window

Reproduces in: 2020.2.0a5, 2020.1.0b4, 2019.3.7f1
Not reproducible: 2019.2.20f1 (Different preview buttons and no undock on right-click)