el-table 在用到 :tree-props的时，对其子组件做删除修改处理时，出现了。children undefind

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数据结构是这样的

{
          id: 1,
          date: "2016-05-02",
          name: "sdsd对数函数的 ",
          levels: 1,
          address: "上海市普陀区金沙江路 1518 弄",
          children: [
            {
              id: 11,
              date: "2016-05-01",
              name: "万二份",
              levels: 2,
              address: "上海市普陀区金沙江路 1519 弄",
              children: [
                {
                  id: 111,
                  date: "2016-05-01",
                  levels: 3,
                  name: "王三",
                  address: "上海市普陀区金沙江路 1519 弄"
                }
              ]
            }
          ]
        },

表单组件

 <el-table
      :data="tableData"
      style="width: 100%;margin-bottom: 20px;"
      row-key="id"
      stripe
      ref="refs" 
      :tree-props="{children: 'children', hasChildren: 'hasChildren'}"
    >

我写的方法是这样的

sortDelet(row) {
      //   console.log(this);
      console.log(row);
      console.log(row.levels);

      if (row.levels * 1 == 1) {
        this.tableData.splice(this.tableData.indexOf(row), 1);
      } else if (row.levels * 1 == 2) {
        // debugger;
        let child1 = [];
        for (let i = 0; i <= this.tableData.length; i++) {
          child1 = this.tableData[i].children;
          for (let j = 0; j < child1.length; j++) {
            if (child1[j].id * 1 == row.id*1) {
              child1.splice(child1.indexOf(child1[j]), 1);
            }
          }
        }
      } else if (row.levels * 1 == 3) {
        let child1 = [];
        let child2 = [];
        for (let i = 0; i <= this.tableData.length; i++) {
         

          child1 = this.tableData[i].children;
          for (let j = 0; j < child1.length; j++) {
            child2 = this.tableData[i].children[j].children;
            for (let k = 0; k < child2.length; k++) {
              if (child2[k].id * 1 == row.id*1) {
                child2.splice(child2.indexOf(child2[k]), 1);
              }
            }
          }
        }
      }
    }

报错是这样的
但是奇怪的是，功能实现了，但是一直报错，
Error in v-on handler: "TypeError: Cannot read property 'children' of undefined"


拜托各位大牛，看一下，谢谢啦

[console.log( )]

let定义只在块级作用域起作用，用var

 let child1 = [];
        let child2 = [];

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非常感谢您的回复，我试了还是一样报错