element UI的Cascader级联选择器,当options为空数组时，下拉框显示问题

Question

问题描述

当options为空数组时，这里的下拉框为什么不显示“无数据”之类的提示，并且高度一直是204px

相关代码

<script src="//unpkg.com/vue/dist/vue.js"></script>
<script src="//unpkg.com/element-ui@2.5.4/lib/index.js"></script>
<div id="app">
<div class="block">
<span class="demonstration">默认 click 触发子菜单</span>
<el-cascader :options="options" v-model="selectedOptions" @change="handleChange">
</el-cascader>
</div>
</div>

var Main = {

data() {
  return {
    options: [],
    selectedOptions: [],
    selectedOptions2: []
  };
},
methods: {
  handleChange(value) {
    console.log(value);
  }
}

};
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')