bugfix

src/components/courseTree/CourseTree.vue

@@ -1137,7 +1137,7 @@ export default {
     },
     activeCourseId() {
       let courseId = this.query.courseId;
-      if (!courseId) {
+      if (!courseId&&this.treeList.length) {
         courseId = this.treeList[0].courseId;
       }
       return courseId;