fix

app/views/tidings/_tiding.json.jbuilder

@@ -4,7 +4,15 @@ json.content tiding.content
 
 json.identifier tiding.identifier
 json.auth_type tiding.container_type == 'ApplyUserAuthentication' ? tiding.container.auth_type : nil
-json.homework_type tiding.container_type == 'HomeworkCommon' ? tiding.container.homework_type : nil
+
+homework_type = nil
+if tiding.container_type == 'HomeworkCommon'
+  homework_type = tiding.container.homework_type rescue nil
+  if homework_type.blank?
+    homework_type = tiding.parent_container.homework_type rescue nil
+  end
+end
+json.homework_type homework_type
 
 json.time tiding.how_long_time
 json.new_tiding tiding.unread?(@onclick_time)