util-app: Account for Medias without URLs in serilize_os_title

RHEL doesn't ship a direct URL, but a custom authentication dialog
instead.
2 jobs for obsessive-compulsive-disorder in 48 minutes and 16 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Test
passed #642609
flatpak
flatpak

00:38:35

 
  Fedora
passed #642610
fedora:rawhide

00:09:41