svtplay: Catch media without any videoReferences

This happens when they publish information about the TV episode before
publishing the video stream. Probably due to some bug in SVT Play. The
web player is also unable the play the video, reporting "Can't play
the program, try again later".

lib/svtplay_dl/service/svtplay.py

@@ -75,6 +75,10 @@ class Svtplay(Service, OpenGraphThumbMixin):
         if options.force_subtitle:
             return
 
+        if len(data["video"].get("videoReferences", [])) == 0:
+            yield ServiceError("Media doesn't have any associated videos (yet?)")
+            return
+
         for i in data["video"]["videoReferences"]:
             parse = urlparse(i["url"])