windows still exists after closeAllSubWindows()

[ravas]

Any idea why a window is found by mdiArea->currentSubWindow()
directly after mdiArea->closeAllSubWindows()?
mdiArea is a class member for a QMainWindow subclass.

The windows appear to have been closed after the function (QMainWindow::closeEvent) returns.
And the next time the function runs it will find the currentSubWindow to be null.

mdiArea->closeAllSubWindows();
qDebug() << mdiArea->subWindowList().length();

mdiArea->closeAllSubWindows();
qDebug() << mdiArea->subWindowList().length();

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If I have 2 sub-windows open,
the debug ouput is 2.

Qt 5.5 / win 7