修复老师角色打包下载所有作业当作业没有附件时报错的BUG

解决方法：页面跳转错误

app/controllers/zipdown_controller.rb

@@ -86,7 +86,7 @@ class ZipdownController < ApplicationController
       end
     end
     if has_file == false
-      render file: 'public/no_file_fond.html.erb' , :layout => 'course_base'
+      render file: 'public/no_file_fond.html' , :layout => 'course_base'
     end
     zipping "#{Time.now.to_i}_#{bid.name}.zip", user_zip_paths, OUTPUT_FOLDER