yii2 kartik FileInput - File input empty
<p>I am using kartik file input widget in a yii2 project.</p>

<p><a href="http://demos.krajee.com/widget-details/fileinput">http://demos.krajee.com/widget-details/fileinput</a></p>

<p>Everything is fine until the update page is accessed where the already uploaded images for a particular post are displayed using the 'initialPreview' option. The preview works, but when the form is submitted, the file input is empty and the form won't validate. <code>Poster Image (256x376) cannot be blank.</code></p>

<pre><code>&lt;?php
     echo $form-&gt;field($model, 'posterImage')-&gt;widget(FileInput::classname(), [
       'options' =&gt; [
        'multiple' =&gt; true,
        'accept' =&gt; 'image/*',
       ],
       'pluginOptions' =&gt; [
         'maxImageWidth' =&gt; 265,
         'maxImageHeight' =&gt; 376,
         'minImageWidth' =&gt; 265,
         'minImageHeight' =&gt; 376,
         'previewFileType' =&gt; 'image',
         'allowedFileExtensions' =&gt; [
          'jpg', 'jpeg'
          ],
          'showUpload' =&gt; false,
          'maxFileSize' =&gt; 200,
          'maxFileCount' =&gt; 1,
          'initialPreview' =&gt; [
            $model-&gt;posterImage ? Html::img($model-&gt;posterImage, ['width' =&gt; '100%']) : NULL,
           ],
           'initialPreviewConfig' =&gt; [
            ['url' =&gt; $model-&gt;posterImage],
            ],
            'initialPreviewAsData' =&gt; false,
            'overwriteInitial' =&gt; true,
              ]
                    ]);
                    ?&gt;
</code></pre>