关于 Vue 的 UI 框架 mint-ui 中组件 checklist 的问题？

[wisej]

无法使用组件 checklist，报错信息：

TypeError: Cannot read property 'length' of undefined
    at Proxy.render (eval at <anonymous> (build.js:805), <anonymous>:9092:46)
    at VueComponent.Vue._render (eval at <anonymous> (build.js:768), <anonymous>:2216:22)
    at VueComponent.updateComponent (eval at <anonymous> (build.js:768), <anonymous>:2609:21)
    at Watcher.get (eval at <anonymous> (build.js:768), <anonymous>:2934:27)
    at new Watcher (eval at <anonymous> (build.js:768), <anonymous>:2926:12)
    at VueComponent.Vue._mount (eval at <anonymous> (build.js:768), <anonymous>:2608:19)
    at VueComponent.Vue$3.$mount (eval at <anonymous> (build.js:768), <anonymous>:6178:15)
    at VueComponent.Vue$3.$mount (eval at <anonymous> (build.js:768), <anonymous>:8549:16)
    at init (eval at <anonymous> (build.js:768), <anonymous>:1740:11)
    at createComponent (eval at <anonymous> (build.js:768), <anonymous>:4174:9)

我在仓库搜这个 issue，有三个跟我一样的问题，可惜只有问题描述就都关闭了。 从报错信息看，是有个变量（应该就是） undefined 却用到了。而且这个变量应该就是 checklist 绑定用到的数组。

<mt-checklist
    title=""
    v-model="item_answer"
    :options="choices_item">
    </mt-checklist>

choices_item 是一个 computed。想问问懂的大佬，为什么会出现 undefined 的情况呢？