调整

app/controllers/courses_controller.rb

@@ -635,7 +635,7 @@ class CoursesController < ApplicationController
         teacher_member = CourseMember.create!(course_id: @course.id, user_id: params[:user_id], role: params[:roles].include?("PROFESSOR") ? 2 : 3)
         # 如果有未审批的申请教师/助教的记录，则修改状态为已审批
         apply_teacher = CourseMessage.where(course_id: @course.id, course_message_id: params[:user_id], status: 0).last
-        apply_teacher.update!(status: 1, apply_user_id: current_user.id)
+        apply_teacher.update!(status: 1, apply_user_id: current_user.id) if apply_teacher.present?
       elsif course_members.exists?(role: %i[PROFESSOR ASSISTANT_PROFESSOR])
         teacher_member = course_members.where(role: %i[PROFESSOR ASSISTANT_PROFESSOR]).take
         if params[:roles].include?("PROFESSOR") || params[:roles].include?("ASSISTANT_PROFESSOR")