Fix bug.

lib/feed_model/cache.rb

@@ -27,8 +27,8 @@ module FeedModel
       unless @skip_callback
         if self.class == Category
           Thread.new do
-            SiteFeedAnnc.where(merge_with_category: self.id.to_s).each do |site_feed_annc|
-              recreate_annc_cache(site_feed_annc)
+            SiteFeed.where(merge_with_category: self.id.to_s).each do |site_feed|
+              recreate_annc_cache(site_feed)
             end
           end
         elsif self.class == SiteFeed