[rygel] engine-gst: Don't crash if dvdreadsrc is missing

[Jens Georg <jensgeorg src gnome org>]

commit 5b10ef81d667ed35dfc5986d56dfedeec431fa76
Author: Jens Georg <mail jensge org>
Date:   Fri Feb 19 16:20:46 2016 +0100

    engine-gst: Don't crash if dvdreadsrc is missing
    
    Signed-off-by: Jens Georg <mail jensge org>

 src/media-engines/gstreamer/rygel-gst-utils.vala |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)
---
diff --git a/src/media-engines/gstreamer/rygel-gst-utils.vala 
b/src/media-engines/gstreamer/rygel-gst-utils.vala
index 5bd5a25..e42b575 100644
--- a/src/media-engines/gstreamer/rygel-gst-utils.vala
+++ b/src/media-engines/gstreamer/rygel-gst-utils.vala
@@ -53,9 +53,15 @@ internal abstract class Rygel.GstUtils {
 
                 src = Gst.parse_bin_from_description (description, true);
             } else if (uri.has_prefix ("dvd://")) {
+                src = ElementFactory.make ("dvdreadsrc", null);
+                if (src == null) {
+                    warning (_("GStreamer element 'dvdreadsrc' not found. DVD support does not work"));
+
+                    return null;
+                }
+
                 var tmp = new Soup.URI (uri);
                 var query = Soup.Form.decode (tmp.query);
-                src = ElementFactory.make ("dvdreadsrc", null);
                 if (query.contains ("title")) {
                     src.title = int.parse (query.lookup ("title"));
                 }