Recognize file name in reference fragment in getPDFFileNameFromURL

The regular expression incorrectly marked a group as capturing.
For `http://example.com/#file.pdf`, the expected result is "file.pdf",
but instead "document.pdf" was returned.

web/ui_utils.js

@@ -371,8 +371,8 @@ function noContextMenuHandler(e) {
  * @return {String} Guessed PDF file name.
  */
 function getPDFFileNameFromURL(url) {
-  var reURI = /^(?:([^:]+:)?\/\/[^\/]+)?([^?#]*)(\?[^#]*)?(#.*)?$/;
-  //            SCHEME      HOST         1.PATH  2.QUERY   3.REF
+  var reURI = /^(?:(?:[^:]+:)?\/\/[^\/]+)?([^?#]*)(\?[^#]*)?(#.*)?$/;
+  //            SCHEME        HOST         1.PATH  2.QUERY   3.REF
   // Pattern to get last matching NAME.pdf
   var reFilename = /[^\/?#=]+\.pdf\b(?!.*\.pdf\b)/i;
   var splitURI = reURI.exec(url);