[banshee] [CoverArtSpec] Support albums without an artist (bgo#612626)

[Alexander Kojevnikov <alexk src gnome org>]

commit 716a646cdf82267096e1569b32900e80ed0441bf
Author: Marijn Ros <marijn mad scientist com>
Date:   Mon Mar 15 20:01:23 2010 +1100

    [CoverArtSpec] Support albums without an artist (bgo#612626)
    
    Signed-off-by: Alexander Kojevnikov <alexander kojevnikov com>

 src/Core/Banshee.Core/Banshee.Base/CoverArtSpec.cs |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/src/Core/Banshee.Core/Banshee.Base/CoverArtSpec.cs b/src/Core/Banshee.Core/Banshee.Base/CoverArtSpec.cs
index 4340e3b..77fb38b 100644
--- a/src/Core/Banshee.Core/Banshee.Base/CoverArtSpec.cs
+++ b/src/Core/Banshee.Core/Banshee.Base/CoverArtSpec.cs
@@ -87,10 +87,15 @@ namespace Banshee.Base
 
         public static string CreateArtistAlbumId (string artist, string album)
         {
-            if (artist == unknown_artist || artist == unknown_artist_tr || album == unknown_album || album == unknown_album_tr) {
+            if (album == unknown_album || album == unknown_album_tr) {
+		// do not attempt to group unknown album tracks together
                 return null;
             }
 
+            if (artist == unknown_artist || artist == unknown_artist_tr) {
+                artist = null;
+            }
+
             string digestible = String.Format ("{0}\t{1}", artist ?? "", album ?? "");
 
             return String.Format ("album-{0}", Digest (digestible));