资源缓存相关BUG修改

app/models/attachment.rb

@@ -686,10 +686,12 @@ class Attachment < ActiveRecord::Base
   #更新时间
   def update_others
     if self.course
+      if self.course.is_a?(::Course)
         self.course.update_course
       end
     end
   end
+end
 
 # Delete the previous articles index in Elasticsearch
 # Attachment.__elasticsearch__.client.indices.delete index: Attachment.index_name rescue nil