[grilo] core: Fix compiler warning

[Juan A. Suarez Romero <jasuarez src gnome org>]

commit df8e6103c5efd11b162c3bfbd772bd334d4ae5b2
Author: Alberto Garcia <agarcia igalia com>
Date:   Wed Mar 20 12:27:45 2013 +0200

    core: Fix compiler warning
    
    gcc complains about 'unknown_keys' being possibly uninitialized when
    media_decorate() is called from queue_add_media().
    
    That probably happens because gcc cannot guarantee that
    g_queue_push_tail() doesn't modify qlement->is_ready.

 src/grl-source.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/grl-source.c b/src/grl-source.c
index 4083b5c..ce5e283 100644
--- a/src/grl-source.c
+++ b/src/grl-source.c
@@ -2038,7 +2038,7 @@ queue_add_media (struct BrowseRelayCb *brc,
                  const GError *error)
 {
   QueueElement *qelement;
-  GList *unknown_keys;
+  GList *unknown_keys = NULL;
 
   if (!brc->queue) {
     brc->queue = g_queue_new ();