example gui applications segfault when using directfb

When using the directfb plugin, the example applications rasterwindow and analogclock segfault in QDirectFbBackingStore::QDirectFbBackingStore(). This is due to the fact that window->handle() is null. That is, QDirectFbBackingStore has been called for a QWindow that had not been created yet.

A similar bug was fixed in the linuxfb plugin (QFbBackingStore::QFbBackingStore()) by commit 3c50917a6ac1ee7fd4707d69a8ca186343c21f91

I've actually tested with the newly released 5.1.1 but bugtracker doesn't allow me to select that yet.