QDockAreaLayoutInfo crashes in restoreState (l. 1978-9) when restoring closed, floating QDockWidget

Inside the constructor of a class inheriting QMainWindow, I create ten QDockWidgets, that are initially docked. Then I save the state of the QMainWindow inside a QByteArray variable

(defaultState)

.
If one of those QDockWidget is undocked and closed, my application crashes at line 1978 of "qdockarealayout.cpp" when I call

restoreState(defaultState);

.

In any other situation (when moving QDockWidgets, closing them without undocking, undocking them without closing...), or if I explicitly call

setFloating(false);

in

QDockWidget::closeEvent

, it works as expected: the main window and docks are properly restored.
Note that I only ran into this problem on Mac OS X. I tested on Linux and Windows, and it seems to work fine.

From what I have seen when debugging, the problem comes from

widget->setFloating(false);

at line 1979 of "qdockarealayout.cpp". After this method is called on a floating, closed QDockWidget, its containing QDockAreaLayoutInfo object is in a bad state. But I didn't manage to track down the problem further.