[rygel] server: Prevent critical on missing information

[Jens Georg <jensgeorg src gnome org>]

commit 84c9c03cf5d873a5e49021c23f101b12b5ebdef9
Author: Jens Georg <mail jensge org>
Date:   Sat Apr 4 23:15:54 2015 +0200

    server: Prevent critical on missing information
    
    Signed-off-by: Jens Georg <mail jensge org>

 src/librygel-server/rygel-media-art-store.vala |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/src/librygel-server/rygel-media-art-store.vala b/src/librygel-server/rygel-media-art-store.vala
index b022716..d55686e 100644
--- a/src/librygel-server/rygel-media-art-store.vala
+++ b/src/librygel-server/rygel-media-art-store.vala
@@ -57,6 +57,12 @@ public class Rygel.MediaArtStore : GLib.Object {
         File file = null;
 
         foreach (var type in MediaArtStore.types) {
+            if (type == "album" && item.album == null && item.artist == null) {
+                continue;
+            } else if (item.artist == null && item.title == null) {
+                continue;
+            }
+
             MediaArt.get_file (item.artist,
                                type == "album" ? item.album : item.title,
                                type,