QDockWidget doesn't properly dock anymore after it was undocked (regression)

If you detach a dockwidget to the floating position, release it, and then try to dock it into the mainwindow again, then it won't properly try to find its place anymore with the latest Qt dlls.
The correct behavior can be seen when undocking the widget and moving it around in the dockarea.

You can test this with the dockwidgets example in the QtCreator.

Best Regards,
Megamouse