修复bug

src/pages/course/details/index.vue

@@ -47,13 +47,13 @@
                         <h4 class="title">{{courseName}}</h4>
                         <div class="desc-wrap">
                             <div class="desc" :class="{active: desShrink}" v-html="description"></div>
-                            <i class="arrow" :class="{active: desShrink}" v-if="description.length > 40">
+                            <i class="arrow" :class="{active: desShrink}" v-if="description && description.length > 40">
                                 <span>...</span>
                                 <img src="@/assets/img/arrow-down.png" alt="" @click="desShrink = !desShrink">
                             </i>
                         </div>
                         <div class="chapters">
-                            <template v-if="videoList.length">
+                            <template v-if="videoList && videoList.length">
                                 <div class="chapter" v-for="(item,index) in videoList" :key="index">
                                     <div class="chapterName">{{item.name}}</div>
                                     <div class="section" v-if="item.subsectionList.length">