修正删除课程的一个bug
修正删除课程的一个bug

hydrogenlee/CourseSelect,Software-622-group/FinalWork,PENGZhaoqing/CourseSelect,jinbaowang/CourseSelect,Software-622-group/FinalWork,courseselect/cs,courseselect/cs,hydrogenlee/CourseSelect,courseselect/cs,PENGZhaoqing/CourseSelect,hydrogenlee/CourseSelect,PENGZhaoqing/CourseSelect,Software-622-group/FinalWork,jinbaowang/CourseSelect,jinbaowang/CourseSelect