title: Error when attempting to parse xhr response text
body: <p>I have downloaded the plugin "Fine Uploader" and initialize it that (according to the examples of the official website) all good except that when wanting to upload the file will not let me, giving me the following error:</p>
  
  <blockquote>
    <p>[Fine Uploader 5.2.1] Error when attempting to parse xhr response text (Unexpected token &lt;)<br>
        fine-uploader.js:249 <br>
        qq.logfine-uploader.js:1837<br>
        qq.basePublicApi.logfine-uploader.js:695 <br>
        qq.bindfine-uploader.js:7845 <br>
        parseResponsefine-uploader.js:7828 <br>
        onUploadOrChunkCompletefine-uploader.js:7789 <br>
        xhr.onreadystatechange</p>
  </blockquote>
  
  <p>this is the only thing I changed from the demos shown on the official website </p>
  
  <pre><code>var galleryUploader = new qq.FineUploader({ 
      element: document.getElementById("fine-uploader-gallery"), 
      template: 'qq-template-gallery', 
      request: { endpoint: '../proyecciones' }, 
      thumbnails: { 
          placeholders: {
              waitingPath: '../fine-uploader/placeholders/waiting-generic.png', 
              notAvailablePath: '../fine-uploader/placeholders/not_available-generic.png' 
          } 
      }, 
      validation: { 
          allowedExtensions: ['jpeg', 'jpg', 'gif', 'png'] 
      } 
  });
  </code></pre>