fix:新商品规格购买，系统自动分班，已存在班级商品，购买只能选择存在班级

src/components/buyCourseModal/index.vue

@@ -106,6 +106,8 @@ export default {
   mounted() {},
   methods: {
     showModal(item) {
+      this.gradeId = ''
+      this.gradeList = []
       this.selectClassModal = true;
       this.goodsDetail = item;
     },