title: Can't get process start variables
body: <p>I'm trying to get process start variables via rest, but I can't receive any start variable.</p>
  
  <p>When i try:</p>
  
  <pre><code>http://192.168.30.1:8080/engine-rest/process-definition/key/invoice/form-variables
  </code></pre>
  
  <p>I got only this:</p>
  
  <pre><code>{}
  </code></pre>
  
  <p>How to get process start variables?</p>