I still get an error:

Debugger entered--Lisp error: (args-out-of-range #<buffer org-mode-blog/posts/blogging-with-org-mode.org> 0 33)

  match-string(1)

I think you need to provide the original string to match-string, so either "let" it or like so:

@@ -1171,7 +1171,7 @@ the file including them will be republished as well."

   (and (eq (org-element-type element) 'keyword)

        (string-match "^\\(\".+?\"\\|\\S-+\\)"

      (org-element-property :value element))

-       (org-remove-double-quotes (match-string 1)))))

+       (org-remove-double-quotes (match-string 1 (org-element-property :value element))))))

     (when included-file

       (add-to-list 'included-files-ctime

    (org-publish-cache-ctime-of-src

with this change it works for me

cheers