[tracker] tracker-extract: Albumartist may be NULL in flac

[Marinus Schraal <mschraal src gnome org>]

commit 375b5a9cc9c038c25ee4e27a38238a36f8188358
Author: Marinus Schraal <mschraal src gnome org>
Date:   Mon Nov 7 14:34:39 2016 +0100

    tracker-extract: Albumartist may be NULL in flac
    
    album_artist is a TrackerResource, but may be NULL: do not just unref
    it.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=774062

 src/tracker-extract/tracker-extract-flac.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/tracker-extract/tracker-extract-flac.c b/src/tracker-extract/tracker-extract-flac.c
index fcdd45a..b137d29 100644
--- a/src/tracker-extract/tracker-extract-flac.c
+++ b/src/tracker-extract/tracker-extract-flac.c
@@ -254,7 +254,7 @@ tracker_extract_get_metadata (TrackerExtractInfo *info)
                tracker_resource_set_relation (metadata, "nmm:musicAlbumDisc", album_disc);
 
                g_object_unref (album_disc);
-               g_object_unref (album_artist);
+               g_clear_object (&album_artist);
        }
 
        tracker_guarantee_resource_title_from_file (metadata, "nie:title", fd.title, uri, NULL);