修复子菜单同级出现子菜单项会同时选中bug

src/assets/scss/_base.scss

    }
    .el-menu {
      > .el-menu-item,
      > .el-submenu .el-submenu__title {
      > .el-submenu > .el-submenu__title {
        color: #fff;
        &:focus,
        &:hover {
        }
      }
      > .el-menu-item.is-active,
      > .el-submenu.is-active .el-submenu__title {
      > .el-submenu.is-active > .el-submenu__title {
        border-bottom-color: mix(#fff, $navbar--background-color, 85%);
      }
      .el-menu-item i,
      text-decoration: none;
    }
    .el-menu-item,
    .el-submenu .el-submenu__title {
    .el-submenu > .el-submenu__title {
      height: 50px;
      line-height: 50px;
    }
    > .el-menu--popup {
      background-color: $sidebar--background-color-dark;
      .el-menu-item,
      .el-submenu .el-submenu__title {
      .el-submenu > .el-submenu__title {
        color: $sidebar--color-text-dark;
        &:focus,
        &:hover {
        background-color: mix(#000, $sidebar--background-color-dark, 15%);
      }
      .el-menu-item.is-active,
      .el-submenu.is-active .el-submenu__title {
      .el-submenu.is-active > .el-submenu__title {
        color: mix(#fff, $sidebar--color-text-dark, 80%);
      }
    }