Make the Jamendo database update work on my machines

The popularity field of the SQL query to add Jamendo albums to the db
sometimes doesn't seem to contain a valid number. This results in lots
of errors like:

amarok: [ERROR__] [MySqlStorage] "GREPME MySQLe query failed! (1054) Unknown column 'nan' in 'field list' on INSERT INTO jamendo_albums ( id, name, description, popularity, cover_url, launch_year, genre, artist_id, mp3_torrent_url, ogg_torrent_url ) VALUES ( 7565, 'The Last Wanderer', '', nan, 'http://api.jamendo.com/get2/image/album/redirect/?id=7565&imagesize=100', 2007, 'New Age', 5639, 'http://api.jamendo.com/get2/bittorrent/file/plain/?album_id=7565&type=archive&class=mp32', 'http://api.jamendo.com/get2/bittorrent/file/plain/?album_id=7565&type=archive&class=ogg3' );"

For those cases I set the popularity field (do we use that anyway?) to 0.

Please test.