element UI 導航欄展開后子菜單寬度多出1px是怎么回事?

1. 復制的官網(wǎng)的項目側(cè)邊導航，不設置el-aside的寬度是沒問題的，但是<el-aside width="200px">后就出問題了。

<el-container>
        <el-aside width="200px">
          <el-row class="tac">

            <el-col :span="24">
              <el-menu
                default-active="2"
                class="el-menu-vertical-demo"
                unique-opened
                @open="handleOpen"
                @close="handleClose"
                background-color="#545c64"
                text-color="#fff"
                active-text-color="#ffd04b">
                <el-submenu index="1">
                  <template slot="title">
                    <i class="el-icon-location"></i>
                    <span>導航一</span>
                  </template>
                  <el-menu-item index="1-1">選項1</el-menu-item>
                  <el-menu-item index="1-2">選項2</el-menu-item>
                </el-submenu>
                <el-submenu index="2">
                  <template slot="title">
                    <i class="el-icon-location"></i>
                    <span>導航一</span>
                  </template>
                  <el-menu-item index="2-1">選項1</el-menu-item>
                  <el-menu-item index="2-2">選項2</el-menu-item>
                </el-submenu>
              </el-menu>
            </el-col>
          </el-row>
        </el-aside>
        <el-main>
          <main-content></main-content>
        </el-main>
      </el-container>