报错 [Vue warn]: Error in directive contextmenu bind hook: "TypeError: Cannot read property '$refs' of undefined"

  <div :class="['box', theme]" v-contextmenu:contextmenu>
    <Tree :data="data1" @on-select-change="treeChange"></Tree>
  </div>
  <v-contextmenu :theme="theme" ref="contextmenu">
    <v-contextmenu-item>菜单1</v-contextmenu-item>
    <v-contextmenu-item>菜单2</v-contextmenu-item>
    <v-contextmenu-item>菜单3</v-contextmenu-item>
  </v-contextmenu>
  
  
  
  import Vue from 'vue'
  import contentmenu from 'v-contextmenu'
  import 'v-contextmenu/dist/index.css'
  import Contextmenu from 'v-contextmenu'
  import ContextmenuItem from 'v-contextmenu'
  Vue.use(contentmenu)
  

求别贴源码地址了。。。我已经翻了很多遍了。。谢谢大佬们。。。