title: APS package: Enum field has empty entry in dropdown
body: <p>In an APS package, I have defined an "account" service to create service users in my application. One of the account's settings is an enum value for the user's role:</p>
  
  <pre><code>&lt;setting type="enum" id="user_role" default-value="2" element-type="enum"&gt;
      &lt;name&gt;User Role&lt;/name&gt;
      &lt;choice id="1"&gt;&lt;name&gt;Administrator&lt;/name&gt;&lt;/choice&gt;
      &lt;choice id="2"&gt;&lt;name&gt;Supporter&lt;/name&gt;&lt;/choice&gt;
  &lt;/setting&gt;
  </code></pre>
  
  <p>This gets shown as a dropdown value in POA, like this:</p>
  
  <p><img src="https://i.stack.imgur.com/nCu0u.png" alt="Screenshot, showing empty entry in dropdown"></p>
  
  <p>So - is there a way to get rid of that empty entry? I think it shouldn't be there, as the setting itself is not labeled as optional. Any ideas?</p>