Foreword: I am watching the background management project of bilibili, the error reporting problems encountered and the solutions

report errors:

Original code:

Modification code:

 <el-menu
    default-active="1-4-1"
    class="el-menu-vertical-demo"
    @open="handleOpen"
    @close="handleClose"
    :collapse="isCollapse"
  >
    <el-menu-item
      v-for="item in noChildren"
      :index="item.path"
      :key="item.path"
    >
      <i :class="'el-icon-' + item.icon"></i>
      <span slot="title">{{ item.label }}</span>
    </el-menu-item>
    <el-submenu
      v-for="item in hasChildren"
      :index="item.path + ''"
      :key="item.path"
    >
      <template slot="title">
        <i :class="'el-icon-' + item.icon"></i>
        <span slot="title">{{ item.label }}</span>
      </template>
      <el-menu-item-group
        v-for="(subItem, subIndex) in item.children"
        :key="item.path"
      >
        <el-menu-item :index="subIndex + ''">{{ subItem.label }}</el-menu-item>
      </el-menu-item-group>
    </el-submenu>
  </el-menu>