title: JIRA API error when trying to pull details when field is empty
body: <p>I am using the JIRA API to pull ticket details and put it in a separate database that I can connect Tableau to.
  My problem is that when pulling in a ticket details (using python) where e.g. it has no priority, that I get an error.
  How do I get around that error? How can I handle this error?</p>
  
  <p>Just currently testing by printing the details on-screen:</p>
  
  <pre><code>for issue in issues:
  if verbose:
              print( "issue.key: ", issue.key );
              print( "issue.fields.project.id: ", issue.fields.project.id );
  </code></pre>
  
  <p>The error I get is:</p>
  
  <blockquote>
    <p>cursor.execute(sql_stmt, (issue.key, issue.fields.issuetype.name,
    issue.fields.project.name, issue.fields.summary,
    issue.fields.updated,issue.fields.priority.name)) AttributeError: type
    object 'PropertyHolder' has no attribute 'priority</p>
  </blockquote>