title: Error in activity expression - Ask array if not empty
body: <p>I try to use following expression in activity in an exclusive Gateway :</p>
  
  <pre><code> ${(MediaScanResult.videoInfo.videoTracks != 'empty' )}
  </code></pre>
  
  <p>videoTracks is an Array. I want to know if this is not empty. </p>
  
  <p>I got following Error Message:</p>
  
  <pre><code>Error while Calling BPMN: org.activiti.engine.ActivitiException: 
  Error while evaluating expression: ${MediaScanResult.videoInfo.videoTracks != 'empty' )}
  </code></pre>
  
  <p>Any Idear how to check this?</p>