fix: 修改bug

src/modules/exam/exam/views/Index.vue

@@ -85,7 +85,8 @@ export default {
     },
     startExam(data) {
       const num = parseInt(data.status)
-      if (data.leave_times > 6) {
+      const leaveTimes = data.leave_times || 0
+      if (leaveTimes > 6) {
         this.$alert('离开考试页面已超过限定次数，考试结束', {
           confirmButtonText: '查看结果',
           callback: action => {