title: What does a genre id "-1" mean?
body: <p>At this moment, a search for <code>http://api.deezer.com/search/album?q=Big%20Sean%20Bounce%20Back</code>, will have some results with a <code>genre_id</code> or <code>-1</code>.</p>
  
  <p>Is there a specific meaning to this 'id'?</p>