Checking isActive() on focusOutEvent causes segmentation fault

The attached test case shows the crash, which happens inside QWindow::isAncestorOf when it is called by QWindow::isActive, due to the focus pointer that is null when the whole application loses the focus. The focus pointer is null in this case because of the return of QGuiApplication::focusWindow().

I have a patch that solves this issue. It is a simple patch, however I am wondering if it should go inside of isActive() or isAncestorOf(). The first alternative seems to be the right one.

I'll submit the change to gerrit and link this Task, so we can discuss about the solution.