ant-design-vue——a-select下拉框值为空字串时，高度偏窄问题

···
<a-select v-model="formData.urgentLevel"   dropdownClassName="selectOption">
       <a-select-option v-for="(item,index) in URGENTLEVEL" :key="index"
           :value="item.code">{{item.name}}</a-select-option>
</a-select>
···

URGENTLEVEL:[{
   code:'01',
   name:' '
},{
   code:'02',
   name:'平急'
}]
···

.ant-select-dropdown-menu-item {  //写在全局处
  height: 30px;
}