Error in nextTick

报错信息

“TypeError: Cannot read property ‘children’ of undefined”

解决：找到使用nextTick的地方，因为在之前数据为空导致的，因此加一个判断在nextTick之前

if (Array.isArray(this.classList) && this.classList.length > 0) {
  that.$nextTick(() => {
    ...
  });
}