EGLFS OpenWFD window creation causes fatal error if display config isn't available

A patch to support two native windows (QWindow) in one QGuiApplication application was provided by Qt (look at the attachment).

It works if an appropriate display configuration (OpenWF device, port, pipeline) is available on system. But in case of the display configuration doesn't exists on the system a code from patch causes fatal error and application stops working.

Suggest to handle this case as just returning the error and let the application itself to decide how to handle it.