最近学习vue全家桶，改写vue-hackernews中异步数据部分，改用vue-resource，结果报错

主要是在app.js中加入了下面两行代码

import VueResource from 'vue-resource'
Vue.use(VueResource);

结果，npm run dev 正常，页面第一次请求正常。但，当刷新页面时报 Internal Error 500，服务器端报

error during render : /top
TypeError: Cannot redefine property: $url
    at Function.defineProperties (<anonymous>)
    at plugin (__vue_ssr_bundle__:4089:12)
    at Function.Vue.use (/Users/gpd/work/vue-hackernews/node_modules/vue/dist/vue.runtime.common.js:3437:14)
    at Object.module.exports.Object.defineProperty.value (__vue_ssr_bundle__:263:45)
    at __webpack_require__ (__vue_ssr_bundle__:21:30)
    at Object.<anonymous> (__vue_ssr_bundle__:4199:63)
    at __webpack_require__ (__vue_ssr_bundle__:21:30)
    at __vue_ssr_bundle__:67:18
    at Object.<anonymous> (__vue_ssr_bundle__:70:10)
    at /Users/gpd/work/vue-hackernews/node_modules/vue-server-renderer/build.js:6346:21

请教大神改如何解？