mdi subwindow needs two mouse clicks to close

When placing two mdi subwindows on top of each other so that the close buttons are aligned, one needs to click tree times on the "close button-area" to close two widgets.

Clicking once will close the topmost subwindow and reveal the second subwindow. As the mouse is already placed on the close button one should only need to click once more to close this window as well. Instead one needs to click twice - once for widget to receive focus/hover event and once to close. The same goes for minimize buttons.