问Vue.js如何修复错误:未捕获TypeError: data.filter不是我代码中的函数？

EN

    itens: {"countcats":2,"countsubcats":7,
            "catsubcatsdata":{
                "15978738e6cd1e":{"title":"Test 1","description":"blablabla",
                    "subcats":{
                        "1597873b1653d9": {"codurl":"t01url","title":"Teste subiten 1","description":""},
                        "1597873bd76c80": {"codurl":"t01url2","title":"Testing sub two","description":""},
                        "1597873c9d4a81": {"codurl":"t01url3","title":"Test sub 3","description":"blablabla 01"},
                        }},
                "15978745b32c1b":{"title":"Loren Ipsun","description":"lamet dectoid samet",
                    "subcats":{
                        "159787464bc887":{"codurl":"maecenas","title":"Maecenas pulvinar","description":"orci non volutpat varius"},
                        "159787472eb5e6":{"codurl":"donecorci ","title":"Donec hendrerit orci","description":""},
                        "15978748b89bca":{"codurl":"massadictum","title":"Nullam eu massa dictum", "description":""},
                        "159787495492f4":{"codurl":"ultricies","title":"Etiam massa arcu","description":"Donec ultricies porttitor augue quis dictum. Quisque efficitur nec sapien eu ultricies"}
                        }}
                }}

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="v-for-sectors">
	<input type="text" placeholder="Search" v-model="searchQuery">

  <ul>
    <li v-for="(value, key) in filteredList">
          <b>{{ value.title }}</b><br>{{ value.description }}
			<ul>
			  <li v-for="(vsub, keysub) in value.subcats"><a v-bind:href="'http://www.teste.com/'+vsub.codurl">{{ vsub.title }} - {{ vsub.description }}</a></li>
			</ul>
    </li>
  </ul>
</div>

<script>
    new Vue({
        el: '#v-for-sectors',
        data: {
            searchQuery: '',
            itens: {"catsubcatsdata":{"15978738e6cd1e":{"title":"Test 1","description":"blablabla","subcats":{"1597873b1653d9":{"codurl":"t01url","title":"Teste subiten 1","description":""},"1597873bd76c80":{"codurl":"t01url2","title":"Testing sub two","description":""},"1597873c9d4a81":{"codurl":"t01url3","title":"Test sub 3","description":"blablabla 01"}}},"15978745b32c1b":{"title":"Loren Ipsun","description":"lamet dectoid samet","subcats":{"159787464bc887":{"codurl":"maecenas","title":"Maecenas pulvinar","description":"orci non volutpat varius"},"159787472eb5e6":{"codurl":"donecorci","title":"Donec hendrerit orci","description":""},"15978748b89bca":{"codurl":"massadictum","title":"Nullam eu massa dictum","description":""},"159787495492f4":{"codurl":"ultricies","title":"Etiam massa arcu","description":"Donec ultricies porttitor augue quis dictum."}}}}}
		},
        computed: {
            filteredList: function () {
              var filterKey = this.searchQuery && this.searchQuery.toLowerCase()
              var data = this.itens.catsubcatsdata
				if (filterKey) {
					data = data.filter(function (row) {
                              return Object.keys(row).some(function (key) {
                                return String(row[key]).toLowerCase().indexOf(filterKey) > -1
                              })
							})
				}
                return data
            }
        }
    });
</script>