Error in callback for watcher "value": "TypeError: Cannot read property 'level' of null"

弄了一个省市县级联el-cascader选择器，发现第二次选择的时候报异常如下图

 网上看到这个文章完美解决 https://blog.csdn.net/weixin_43043994/article/details/100303097

我是用了加了key，参考如下我对el-cascader二次封装

<template>
  <div class="definition-cascader">
    <el-cascader
      :key="isRescourceShow"
      v-model="valueFromFather"
      style="100%"
      :options="unitData"
      :props="propsFromFather"
      :placeholder="placeholder"
      :size="size"
      :filterable="filterable"
      :clearable="clearable"
      :show-all-levels="false"
      :filter-method="filterMethod"
      @change="onChange"
    ></el-cascader>
  </div>
</template>


<script>
export default {
  name: 'DefinitionCascader',
  props: {
    // source: {
    //   type: String,
    //   required: true
    // },
    props: {
      type: Object,
      default() {
        return {
          multiple: false,
          checkStrictly: true,
          value: 'id',
          label: 'fullname'
        }
      }
    },
    placeholder: {
      type: String,
      default: '请选择发起单位'
    },
    unitData: Array,
    value: {
      type: [String, Number, Array],
      default: ''
    },
    checkStrictly: {
      type: Boolean,
      default: true
    },
    mustSearchKeyword: {
      type: Boolean,
      default: false
    },
    size: {
      type: String,
      default: 'small'
    },
    clearable: {
      ype: Boolean,
      default: true
    },
    filterable: {
      type: Boolean,
      default: true
    },
  },
  data() {
    return {
      searchKeyword: '',
      isRescourceShow: 0,
      valueFromFather: this.value,
      propsFromFather: this.props
    }
  },
  watch: {
    value(v) {
      this.valueFromFather = v
    },
    unitData(){
      ++this.isRescourceShow
    }
  },
  methods: {
    onChange(v) {
      this.$emit('input', v)
    },
    filterMethod(node, keyword) {
      return node.text.includes(keyword) || keyword.includes(node.text)
    }
  }
}
</script>




<style>
.el-input__inner{
  padding: 0 8px;
}
.el-cascader-menu__wrap {
  height: 300px;
}
</style>