fix empty files

app/controllers/announcement_feeds_controller.rb

@@ -118,7 +118,7 @@ class AnnouncementFeedsController < ApplicationController
 				b = {}
 				b["description_translations"] = bf.description_translations
 				b["title_translations"] = bf.title_translations
-				b["url"] = "#{request.base_url}" + bf.file.url
+				b["url"] = ("#{request.base_url}" + bf.file.url rescue "")
 				a["bulletin_files"] << b
 			end
 			all_anns << a