[rhythmbox] grilo: fix crash due NULL url from GrlMedia

[Victor Toso de Carvalho <victortoso src gnome org>]

commit 3e986dd5c959b8d5ec3b5b2cffa72f81323d8cbe
Author: Victor Toso <me victortoso com>
Date:   Fri May 13 23:16:31 2016 +0200

    grilo: fix crash due NULL url from GrlMedia
    
     #0 g_str_hash (v=0x0) at ghash.c:1876
     #1 in g_hash_table_lookup_node (hash_return=<synthetic pointer>,
        key=0x0, hash_table=0x604640) at ghash.c:375
     #2 g_hash_table_lookup (hash_table=0x604640, key=key entry=0x0) at ghash.c:1147
     #3 in rb_refstring_find (init=0x0) at rb-refstring.c:122
     #4 in rhythmdb_entry_lookup_by_location (db=0x76a490, uri=<optimized out>)
        at rhythmdb.c:4036
     #5 in create_entry_for_media (container=0x0, data=0xcb5360,
        entry_type=<optimized out>, db=0x76a490) at rb-grilo-source.c:553
    
    https://bugzilla.gnome.org/show_bug.cgi?id=766392

 plugins/grilo/rb-grilo-source.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)
---
diff --git a/plugins/grilo/rb-grilo-source.c b/plugins/grilo/rb-grilo-source.c
index 22a9d11..b57e4a6 100644
--- a/plugins/grilo/rb-grilo-source.c
+++ b/plugins/grilo/rb-grilo-source.c
@@ -549,8 +549,14 @@ create_entry_for_media (RhythmDB *db, RhythmDBEntryType *entry_type, GrlData *da
 {
        RhythmDBEntry *entry;
        RBGriloEntryData *entry_data;
+       const gchar *url;
 
-       entry = rhythmdb_entry_lookup_by_location (db, grl_media_get_url (GRL_MEDIA (data)));
+       url = grl_media_get_url (GRL_MEDIA (data));
+       if (url == NULL) {
+               return NULL;
+       }
+
+       entry = rhythmdb_entry_lookup_by_location (db, url);
        if (entry != NULL) {
                return entry;
        }