Deal with NULL gport in virt_viewer_app_set_connect_info()
    
    virt_viewer_app_set_connect_info() has a debug statement printing
    gport/gtlsport. It checks that gtlsport is not NULL before printing it,
    but makes no similar check for gport. Since it's possible to get a NULL
    gport when using ovirt:// after the previous commit, it's better to check
    it too.