Fix bug.

lib/bulletin_model/cache.rb

@@ -4,7 +4,7 @@ module BulletinModel
     extend ActiveSupport::Concern
     included do
       after_save :do_before_save
-      after_destroy :do_before_save
+      before_destroy :do_before_save
     end
     def do_before_save
       if self.class == SubPart