title: node to traverse cannot be null (Hibernate SQL)
body: <p>I'm performing a SQL query through hibernate, which looks like:</p>
  
  <pre><code>SELECT thi 
  FROM track_history_items thi 
  JOIN artists art 
    ON thi.artist_id = art.id 
  WHERE thi.type = "TrackBroadcast" 
  GROUP BY art.name 
  ORDER thi.createdAt DESC
  </code></pre>
  
  <p>but I'm getting the message that 'Node to traverse cannot be null!'.  Anyone know what could be causing this?</p>
  
  <p>--<strong>EDIT</strong>--</p>
  
  <p>I'm pretty sure that this problem is being caused by the possibility of artist_id to be null.  However, I can't prevent this, so can I just skip the rows track_history_item rows which have a null artist_id?</p>