fix bug

app/controllers/exercises_controller.rb

@@ -1291,6 +1291,7 @@ class ExercisesController < ApplicationController
           @page  = params[:page]  || 1
           @limit = params[:limit] || 20
           @exercise_users_list = @exercise_users_list.page(@page).per(@limit)
+          tip_exception(403,"无权限操作")
           respond_to do |format|
             format.json
             format.xlsx{