[tracker] libtracker-extract: fix crash when running unit tests

[Tim Lunn <timl src gnome org>]

commit ad71e5e577b45e605e94278c4ba32e589db2f255
Author: Tim Lunn <tim feathertop org>
Date:   Mon Dec 29 09:14:36 2014 +1100

    libtracker-extract: fix crash when running unit tests
    
    media_art_process is not set when running tracker-extract-info tests
    
    https://bugzilla.gnome.org/show_bug.cgi?id=742035

 src/libtracker-extract/tracker-extract-info.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/libtracker-extract/tracker-extract-info.c b/src/libtracker-extract/tracker-extract-info.c
index cf578db..de2c594 100644
--- a/src/libtracker-extract/tracker-extract-info.c
+++ b/src/libtracker-extract/tracker-extract-info.c
@@ -144,7 +144,8 @@ tracker_extract_info_unref (TrackerExtractInfo *info)
                g_free (info->where_clause);
 
 #ifdef HAVE_LIBMEDIAART
-               g_object_unref (info->media_art_process);
+               if (info->media_art_process)
+                       g_object_unref (info->media_art_process);
 #endif
 
                g_slice_free (TrackerExtractInfo, info);