<!-- generated by https://eleme-issue.surge.sh DO NOT REMOVE -->Nuxt version
1.3.0
Vue version
2.5.13
OS/Browsers version
64.0.3282.167
Reproduction Link
https://github.com/xachary/nuxt-spa-style-url-build-error
Steps to reproduce
install dependencies
$ npm install
serve with hot reload at localhost:3000
$ npm run dev-spa
build for production and launch server at localhost:3001
$ npm run build-spa
$ npm run start-spa
What is Expected?
'dev version' and 'build version' is both ok.
What is actually happening?
You can see 'build version' showing error message.

But if you delete one of 'background-image: url('../assets/img.png');' in '/pages/index.vue', build again, then you can see 'build version' is ok again.

<!-- generated by https://eleme-issue.surge.sh DO NOT REMOVE --><!--cmty--><!--cmty_prevent_hook--><div align="right"><sub><em>This question is available on <a href="https://nuxtjs.cmty.io">Nuxt.js</a> community (<a href="https://nuxtjs.cmty.io/nuxt/nuxt.js/issues/c2531">#c2531</a>)</em></sub></div>