Laravel 5.4 Files is true but still giving getClientOriginalExtension() on null error

as i said on title, turned 'files' true but still giving function getClientOriginalExtension() on null error.

form;

<div class="form-group">
 <div class="col-md-10">
  <label>create article</label>
   <textarea id="article-ckeditor" name="content" placeholder="Write your message.." class="form-control ckeditor"></textarea>
 </div>
</div>
    

 <div class="form-group">
  <div class="col-xs-10">
   <label>
Publish
   </label>
<input type="submit" class="btn-success">
</div>
</div>

and my controller

        $request->all();
        $head = $request->input('head');
        $content = $request->input('content');
        $keywords = $request->input('keywords');
        $featured=$request->input('post_featured');

        $photoName = $featured . '.' . rand(11111, 99999) . '.' . $request->post_featured->getClientOriginalExtension();
        $request->post_featured->move(public_path('uploads'), $photoName);
        News::create(array('head' => $head, 'content' => $content, 'keywords' => $keywords,'post_featured'=>$photoName));

via Chebli Mohamed