ElementUI中el-radio再次点击取消选中

<el-radio-group v-model="radio2">
  <el-radio @click.native.prevent="clickitem(3)" :label="3"> 备选项</el-radio>
  <el-radio @click.native.prevent="clickitem(6)" :label="6"> 备选项</el-radio>
  <el-radio @click.native.prevent="clickitem(9)" :label="9"> 备选项</el-radio>
</el-radio-group>
          
clickitem (e) {
  e === this.radio2 ? this.radio2 = '' : this.radio2 = e
},