[tracker] tracker-extract: Only extract media art if artist or title is known

[Philip Withnall <pwithnall src gnome org>]

commit d7159fe94444ab417097997e6ebe44804c9b6a41
Author: Philip Withnall <philip withnall collabora co uk>
Date:   Tue Apr 21 08:14:12 2015 +0100

    tracker-extract: Only extract media art if artist or title is known
    
    media_art_process_*() require at least one of the track’s artist and
    title to be specified, and will fail an assertion precondition if both
    are NULL.
    
    Other tracker-extract-*.c media backends already do this check, but it
    was missing from the GStreamer extractor.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=748227

 src/tracker-extract/tracker-extract-gstreamer.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/src/tracker-extract/tracker-extract-gstreamer.c b/src/tracker-extract/tracker-extract-gstreamer.c
index bc84a13..af4a408 100644
--- a/src/tracker-extract/tracker-extract-gstreamer.c
+++ b/src/tracker-extract/tracker-extract-gstreamer.c
@@ -1647,7 +1647,9 @@ tracker_extract_gstreamer (const gchar          *uri,
                                  graph);
 
 #ifdef HAVE_LIBMEDIAART
-               if (extractor->media_art_type != MEDIA_ART_NONE) {
+               if (extractor->media_art_type != MEDIA_ART_NONE &&
+                   (extractor->media_art_artist != NULL ||
+                    extractor->media_art_title != NULL)) {
                        GError *error = NULL;
                        gboolean success = TRUE;