调整

app/controllers/student_works_controller.rb

@@ -206,7 +206,7 @@ class StudentWorksController < ApplicationController
     @current_user = current_user
     @work_members = @homework.homework_type != "group" ? [] : @homework.student_works.where.not(user_id: @work.user_id).
         where(group_id: @work.group_id).includes(:user)
-    @attachments = @work.attachments.where.not(attachtype: 7)
+    @attachments = @work.attachments.where("attachtype != 7 or attachtype is null")
   end
 
   # 判断项目是否已有其他作品关联上了