Revert "[fix] Added guard to loading PDF viewer"

This reverts commit 184d650 which
doesn't fix anything but suppresses messages about the error that is
actually occurring

app/helpers/pdfjs/viewer_helper.rb

@@ -177,10 +177,7 @@ def pdf_viewer(filename, options={})
     
       <script type="text/javascript">
         document.addEventListener('DOMContentLoaded', function() {
-          var PDFView = PDFView || {}
-          if (PDFView.open) {
-            PDFView.open(#{filename.to_json});
-          }
+          PDFView.open(#{filename.to_json});
         }, true);
       </script>
       HTML