Quickly undocking a tab can sometimes cause the editor to freeze for a short time

Quickly undocking a window from the main editor window can sometimes result in a large black rectangle appearing, most likely representing the resulting window, and freezing the editor for a short period.

Frequency: 1/10

1. Open a project
2. Open an asset editor window (I.E. Open a material)
3. If it isn't already, dock the new tab into the main window.
4. Click on the new tab and immediately move the mouse down away from the main window, as if you were undocking the tab. Please note that this has be very quick and holding the mouse cursor shouldn't be involved.
   Result: The tab becomes undocked but a large black rectangle appears, representing the resulting window, and freezes the editor for a short time.
   Expected: The tab should undock without any issues.