Quickly docking tab into the main window can cause duplicate tabs to appear

When you quickly dock a tab to the main window, you can sometimes end up with 2 identical tabs. This causes some weird behavior, such as every action being done in one window being replicated in the other. If the undocked window is closed, it can cause the tabs in the main window to become dysfunctional.

Note: While this does happen in 4.11.2, the result is a bit different in that the duplicate window shows up undocked and is extremely small.

1. Open a project
2. Open an asset editor window (I.E. Open a material)
3. If it isn't already, undock the new tab from the main window.
4. Click on the new tab and immediately move the mouse up towards the main window, as if you were docking the tab. Please note that this has be very quick and holding the mouse cursor shouldn't be involved.
   Result: The tab docks but stays as an independent window as well
   Expected: The tab should dock and the existing window should disappear