[tracker] Fix GuPNP-DLNA extractor, genre can be NULL too

[Philip Van Hoof <pvanhoof src gnome org>]

commit 3998c2294d3d4cc7d68a8624b5edb3829fa88794
Author: Philip Van Hoof <philip codeminded be>
Date:   Mon Dec 13 14:27:21 2010 +0100

    Fix GuPNP-DLNA extractor, genre can be NULL too

 src/tracker-extract/tracker-extract-gupnp-dlna.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/tracker-extract/tracker-extract-gupnp-dlna.c b/src/tracker-extract/tracker-extract-gupnp-dlna.c
index ccdf664..0227a5d 100644
--- a/src/tracker-extract/tracker-extract-gupnp-dlna.c
+++ b/src/tracker-extract/tracker-extract-gupnp-dlna.c
@@ -594,7 +594,7 @@ extract_metadata (MetadataExtractor      *extractor,
 		}
 
 		gst_tag_list_get_string (extractor->tags, GST_TAG_GENRE, &genre);
-		if (g_strcmp0 (genre, "Unknown") != 0) {
+		if (genre && g_strcmp0 (genre, "Unknown") != 0) {
 			tracker_sparql_builder_predicate (metadata, "nfo:genre");
 			tracker_sparql_builder_object_unvalidated (metadata, genre);
 		}