[tracker] tracker-extract-gstreamer: Fixed missing const for GstStructure compiler warning

[Martyn James Russell <mr src gnome org>]

commit 90b53d593ad3500f3aeb7691bd39247963cc4d17
Author: Martyn Russell <martyn lanedo com>
Date:   Thu Jul 11 19:03:22 2013 +0100

    tracker-extract-gstreamer: Fixed missing const for GstStructure compiler warning

 src/tracker-extract/tracker-extract-gstreamer.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/tracker-extract/tracker-extract-gstreamer.c b/src/tracker-extract/tracker-extract-gstreamer.c
index 17f3f61..5fa099f 100644
--- a/src/tracker-extract/tracker-extract-gstreamer.c
+++ b/src/tracker-extract/tracker-extract-gstreamer.c
@@ -483,7 +483,7 @@ get_embedded_media_art (MetadataExtractor *extractor)
 
                if (have_sample) {
                        GstBuffer *buffer;
-                       GstStructure *info_struct;
+                       const GstStructure *info_struct;
                        gint type;
 
                        buffer = gst_sample_get_buffer (extractor->sample);