title: Collabora/Code docker install not loading document, throwing JavaScript error
body: <p>I've downloaded and run the Collabora/Code docker image using the following:</p>
  <pre><code>    docker run -t -d -p 127.0.0.1:9980:9980 -e &quot;domain=localhost&quot; -e &quot;username=admin&quot; -e &quot;password=S3cRet&quot; -e --restart always collabora/code
  </code></pre>
  <p>I've also created a local WOPI API that exposes the 4 required endpoints, and I can hit those successfully in the browser/Postman/etc. Whenever I try to access Collabora with a document specified I get the following error:</p>
  <p>URL: http://localhost:9980/loleaflet/7151e02/loleaflet.html?WOPISrc=http://localhost:5001/wopi/files/test123</p>
  <pre><code>    VM682:1 Uncaught SyntaxError: Unexpected token o in JSON at position 1
          at JSON.parse (&lt;anonymous&gt;)
          at PostMessageReadyListener (loleaflet.html?WOPISrc=http://localhost:5001/wopi/files/test:23)
  </code></pre>
  <p>Viewing that code in dev tools shows it's failing on the JSON.parse() line. The e.data object isn't a string, and it also doesn't include a MessageId property.</p>
  <pre><code>      window.WOPIpostMessageReady = false;
        var PostMessageReadyListener = function(e) {
          if (!(e &amp;&amp; e.data))
              return;
          var msg = JSON.parse(e.data);
          if (msg.MessageId === 'Host_PostmessageReady') {
            window.WOPIPostmessageReady = true;
            window.removeEventListener('message', PostMessageReadyListener, false);
          }
        };
  </code></pre>
  <p>Is this an issue with Collabora? Something I didn't configure correctly?</p>