fix error

app/controllers/announcement_feeds_controller.rb

@@ -7,6 +7,7 @@ class AnnouncementFeedsController < ApplicationController
 	    enddt = params[:end].blank? ? nil : params[:end]
 	    dt = params[:date].blank? ? nil : params[:date]
 		feed_cache = BulletinFeedCache.where(uid: uid, start: startdt, end: enddt, date: dt)
+		feed_cache_old = feed_cache.all_of([{:invalid_date.ne=>nil},{:invalid_date.lte => Time.now}]).last
 		feed_cache.all_of([{:invalid_date.ne=>nil},{:invalid_date.lte => Time.now}]).destroy
 		count = feed_cache.count
 	    if count > 1
@@ -16,6 +17,7 @@ class AnnouncementFeedsController < ApplicationController
 		anns = ''
 		if feed_cache.nil?
 			anns = BulletinFeed.where(uid: uid).first.generate_one_cache_timeout(startdt: startdt,enddt: enddt,dt: dt,base_url: request.base_url,timeout: 20)
+			anns = (feed_cache_old.content rescue "") if anns.nil?
 		else
 			anns = feed_cache.content
 		end

app/models/bulletin_feed.rb

@@ -47,7 +47,7 @@ class BulletinFeed
       end
     rescue=> e
       puts [e,e.backtrace]
-      ""
+      nil
     end
   end
   def generate_one_cache(startdt: nil,enddt: nil,dt: nil, base_url: nil)