[bongo-patches] Fix bugs caused by `unknown'

[Daniel Jensen]

Some artist and album fields have `unknown' values. This patch adds
tests in a few infoset reader functions, where `unknown' causes them
to signal an error, which in turn makes `bongo-lastfm-submit' fail
silently. (Ugh!)

diff -Naur bongo-old/bongo.el bongo-new/bongo.el
--- bongo-old/bongo.el  2007-01-08 14:26:29.000000000 +0100
+++ bongo-new/bongo.el  2007-01-08 16:13:11.000000000 +0100
@@ -1828,11 +1828,20 @@
                          file-name)))))))
 
 (defun bongo-infoset-artist-name (infoset)
-  (bongo-alist-get (bongo-alist-get infoset 'artist) 'name))
+  (let ((data (bongo-alist-get infoset 'artist)))
+    (unless (eq data 'unknown)
+      (bongo-alist-get data 'name))))
+
 (defun bongo-infoset-album-year (infoset)
-  (bongo-alist-get (bongo-alist-get infoset 'album) 'year))
+  (let ((data (bongo-alist-get infoset 'album)))
+    (unless (eq data 'unknown)
+      (bongo-alist-get data 'year))))
+
 (defun bongo-infoset-album-title (infoset)
-  (bongo-alist-get (bongo-alist-get infoset 'album) 'title))
+  (let ((data (bongo-alist-get infoset 'album)))
+    (unless (eq data 'unknown)
+      (bongo-alist-get data 'title))))
+
 (defun bongo-infoset-track-index (infoset)
   (bongo-alist-get (bongo-alist-get infoset 'track) 'index))
 (defun bongo-infoset-track-title (infoset)