element table 多選時只選擇了一些，不顯示選擇部分的圖標

<el-table
    ref="multipleTable"
    :data="tableData"
    :row-key="index"
    tooltip-effect="dark"
    style="width: 100%"
    @selection-change="handleSelectionChange">
    <el-table-column
      type="selection"
      width="55">
    </el-table-column>
    <el-table-column
      label="日期"
      width="120">
      <template slot-scope="scope">{{ scope.row.date }}</template>
    </el-table-column>
    <el-table-column
      prop="name"
      label="姓名"
      width="120">
    </el-table-column>
    <el-table-column
      prop="address"
      label="地址"
      show-overflow-tooltip>
    </el-table-column>
  </el-table>

去除:row-key="index"，部分選擇圖標選就恢復正常