修改左侧菜单icon-svg传null错误bug

src/views/main-sidebar-sub-menu.vue

    :index="menu.menuId + ''"
    :popper-class="'site-sidebar--' + sidebarLayoutSkin + '-popper'">
    <template slot="title">
      <icon-svg :name="menu.icon" class="site-sidebar__menu-icon"></icon-svg>
      <icon-svg :name="menu.icon || ''" class="site-sidebar__menu-icon"></icon-svg>
      <span>{{ menu.name }}</span>
    </template>
    <sub-menu
    </sub-menu>
  </el-submenu>
  <el-menu-item v-else :index="menu.menuId + ''" @click="gotoRouteHandle(menu)">
    <icon-svg :name="menu.icon" class="site-sidebar__menu-icon"></icon-svg>
    <icon-svg :name="menu.icon || ''" class="site-sidebar__menu-icon"></icon-svg>
    <span>{{ menu.name }}</span>
  </el-menu-item>
</template>

src/views/main.vue

        }).then(({data}) => {
          if (data && data.code === 0) {
            this.loading = false
            this.userId = data.user.userId || ''
            this.userName = data.user.username || ''
            this.userId = data.user.userId
            this.userName = data.user.username
          }
        })
      }