bug fixes

src/modules/viewer/index.vue

@@ -116,7 +116,7 @@ export default {
         ]
       }
       // 课程大作业
-      if (this.detail.curriculum.curriculum_essay) {
+      if (this.detail.curriculum && this.detail.curriculum.curriculum_essay) {
         customeChapter.children.unshift({ name: this.$t('viewerMain.courseWork'), id: 'course_work', type: 99 })
       }
       // 课程考试