Fix bug in MainWindow::setActiveWindow
Fix bug in MainWindow::setActiveWindow

The method MainWindow::setActiveWindow() must not automatically add a view to the mdi area if it's not part of it because this causes a crash when trying to make a fullscreen window or undock a view.
Instead the calling instance must explicitly call MainWindow::addWindow where needed.

Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master