点击Dropdown 下拉菜单，没有出现菜单栏但是当我把DropDown所在的组件单独拎出来展示，就可以正常显示

而且查看组件，未显示的时候，也是能看到有DropDownMenu组件在的

<div>
    <el-dropdown split-button type="primary" @click="handleClick">
      更多菜单
      <template v-slot:dropdown>
        <el-dropdown-menu>
          <el-dropdown-item
            ><el-button type="primary" icon="el-icon-check"
              >修改账户</el-button
            ></el-dropdown-item
          >
          <el-dropdown-item
            ><el-button type="success" icon="el-icon-check"
              >退出</el-button
            ></el-dropdown-item
          >
          <el-dropdown-item>双皮奶</el-dropdown-item>
          <el-dropdown-item>蚵仔煎</el-dropdown-item>
        </el-dropdown-menu>
      </template>
    </el-dropdown>
  </div>