Menu组件报错：TypeError: Cannot read property ‘isRootMenu‘ of undefined

Menu组件报错：TypeError: Cannot read property ‘isRootMenu’ of undefined

父组件：

 <a-menu
      :selected-keys="selectedKeys"
      :opnekeys="openKeys"
      mode="inline"
      theme="dark"
      class="menu"
      @click="menuClick"
    >
      <template v-for="item in getrouters">
        <SidebarItem   //调用子组件
          v-if="item.children && !item.hidden"
          :key="item.path"
          :sidebarItem="item"
        ></SidebarItem>

        <a-menu-item
          v-if="!item.children && !item.hidden"
          :key="item.path"
          class="ant-menu-item"
        >
          <router-link :to="item.path">
            <a-icon :type="item.meta.icon" />
            <span>{{ item.meta.title }}</span>
          </router-link>
        </a-menu-item>
      </template>
    </a-menu>

子组件： 使用函数式组件

<template functional>
      <a-sub-menu
        :key="props.sidebarItem.path"
        class="ant-menu-submenu"
      >
        <span slot="title">
          <a-icon type="appstore" /><span>{{ props.sidebarItem.meta.title }}</span>
        </span>
        <template v-for="it in props.sidebarItem.children">
         <SidebarItem
          v-if="it.children && !it.hidden"
          :key="it.path"
          :sidebarItem="it"
        ></SidebarItem>
        <a-menu-item
          v-else
          :key="it.path"
          class="ant-menu-item"
        >
        <router-link :to="props.sidebarItem.path + '/' + it.path">
          <span>{{ it.meta.title }}</span>
           </router-link>
        </a-menu-item>
        </template>
       
      </a-sub-menu>
</template>