props传值遇Cannot read property getAttribute of undefined异常

今有一个echarts 图标的子组件使用watch 监听接受父组件传入的data，而在父组件页面再次根据日期筛选数据，重新传入子组件进行图表重绘时老实会提示报错

vue.runtime.esm.js?6e6d:619 [Vue warn]: Error in callback for watcher "chartData": "TypeError: Cannot read property 'getAttribute' of undefined"

found in

原来是异步加载数据切换的锅，watch 中是一个异步函数，再监听到值变化后，真正的值其实并未返回

  watch: {
    chartData(val) {
      if (val) {
        this.chartParentShow = true
        this.$nextTick(() => {
          this.drawLine(val)
        })
      } else {
        this.chartParentShow = false
      }
    }
  },