title: yii2 ckeditor Image source URL is missing
body: <p>I'm using this ckeditor extension for yii2 <a href="https://packagist.org/packages/wadeshuler/yii2-ckeditor-cdn" rel="nofollow noreferrer">https://packagist.org/packages/wadeshuler/yii2-ckeditor-cdn</a></p>
  
  <p>I created directories backend/web/uploads/images and gave them rights 777</p>
  
  <p>I configured backend/config/main.php like this</p>
  
  <pre><code>'modules' =&gt; [
          'ckeditor' =&gt; [
              'class' =&gt; 'wadeshuler\ckeditor\Module',    // required and dont change!!!
  
              'uploadDir' =&gt; '@app/web/uploads',    // must be file path (required when using filebrowser*BrowseUrl below)
              'uploadUrl' =&gt; '@web/uploads',        // must be valid URL (required when using filebrowser*BrowseUrl below)
  
              // These are basically passed to the `CKEDITOR.replace()`
              'widgetClientOptions' =&gt; [
  
                  'filebrowserImageBrowseUrl' =&gt; '/ckeditor/default/image-browse',
                  'filebrowserImageUploadUrl' =&gt; '/ckeditor/default/image-upload',
              ]
          ],
  
      ],
  </code></pre>
  
  <p>Put in the form </p>
  
  <pre><code>use wadeshuler\ckeditor\widgets\CKEditor;
  &lt;?= $form-&gt;field($model, 'body')-&gt;widget(CKEditor::className()) ?&gt;
  </code></pre>
  
  <p>And when I upload an image and click "Send it to the server" it doesn't upload and when I click "ok" it says  Image source URL is missing.</p>
  
  <p>Maybe someone has faced this problem before?
  By the way, if I remove these lines</p>
  
  <pre><code>//'uploadDir' =&gt; '@app/web/uploads',    // must be file path (required when using filebrowser*BrowseUrl below)
          //'uploadUrl' =&gt; '@web/uploads',        // must be valid URL (required when using filebrowser*BrowseUrl below)
  </code></pre>
  
  <p>Nothing is changed. The same mistake.</p>