[grilo] Fix "non-void function should return a value" for clang

[Ting-Wei Lan <lantw src gnome org>]

commit d4ed03666cbac31ee393ae7a4709572611b3a38d
Author: Ting-Wei Lan <lantw src gnome org>
Date:   Thu Dec 4 02:01:38 2014 +0800

    Fix "non-void function should return a value" for clang
    
    https://bugzilla.gnome.org/show_bug.cgi?id=741081

 src/data/grl-media-audio.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/data/grl-media-audio.c b/src/data/grl-media-audio.c
index 3f4ab4f..5dad9ad 100644
--- a/src/data/grl-media-audio.c
+++ b/src/data/grl-media-audio.c
@@ -507,7 +507,7 @@ grl_media_audio_get_mb_album_id (GrlMediaAudio *audio)
 const gchar *
 grl_media_audio_get_mb_artist_id (GrlMediaAudio *audio)
 {
-  g_return_if_fail (GRL_IS_MEDIA_AUDIO (audio));
+  g_return_val_if_fail (GRL_IS_MEDIA_AUDIO (audio), NULL);
   return grl_data_get_string (GRL_DATA (audio), GRL_METADATA_KEY_MB_ARTIST_ID);
 }