title: Vuetify & Webpack Encore compilation error
body: <p>I created (currently standalone) and API and a VueJs (with Vuetify) App and wanted to combine both using the webpack encore bundle for Symfony.</p>
  
  <p>But when I want to build the frontend app, I get this error when executing <code>yarn run encore dev</code>:</p>
  
  <pre><code>(node:12500) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'length' of undefined
      at items.forEach.item (/Users/pguetschow/Projects/hosting-tool/node_modules/vuetify-loader/lib/loader.js:21:60)
      at Set.forEach (&lt;anonymous&gt;)
      at Object.getMatches (/Users/pguetschow/Projects/hosting-tool/node_modules/vuetify-loader/lib/loader.js:16:9)
      at Object.module.exports (/Users/pguetschow/Projects/hosting-tool/node_modules/vuetify-loader/lib/loader.js:106:64)
      at process._tickCallback (internal/process/next_tick.js:68:7)
  (node:12500) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
  (node:12500) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
  </code></pre>
  
  <p>This is my <code>webpack.config.js</code></p>
  
  <pre><code>const Encore = require('@symfony/webpack-encore');
  const VuetifyLoaderPlugin = require('vuetify-loader/lib/plugin');
  
  Encore
      .setOutputPath('public/build/')
      .setPublicPath('/build')
      .cleanupOutputBeforeBuild()
      .enableSourceMaps(!Encore.isProduction())
      .cleanupOutputBeforeBuild()
      .addEntry('js/main', './assets/js/main.js')
      .enableVueLoader()
      .enableBuildNotifications(true)
      .addPlugin(new VuetifyLoaderPlugin())
  ;
  module.exports = Encore.getWebpackConfig();
  </code></pre>
  
  <p>Any idea? The standalone app is working fine, I simply moved it to the assets/js folder. I require vuetify-loader ^1.2.2 for this.</p>
  
  <p>And this is my  <code>main.js</code>:</p>
  
  <pre><code>import Vue from 'vue'
  import App from './App.vue'
  import Vuetify from 'vuetify/lib'
  import MultiFiltersPlugin from './plugins/MultiFilters'
  
  import 'vuetify/src/stylus/app.styl'
  import 'material-design-icons-iconfont/dist/material-design-icons.css'
  import 'vuetify/dist/vuetify.min.css'
  
  Vue.use(MultiFiltersPlugin);
  Vue.use(Vuetify, {
      iconfont: 'md',
  });
  
  new Vue({render: h =&gt; h(App),}).$mount('#app');
  </code></pre>