title: Upgrade from Angular 5.2 to 6.1
body: <p>I am upgrading to Angular 6, but it looks like i get an error when running ng serve or ng build.</p>
  
  <p>I do get the following error </p>
  
  <blockquote>
    <p>Cannot destructure property 'createHash' of 'undefined' or 'null'.
        TypeError: Cannot destructure property 'createHash' of 'undefined' or 'null'.
            at Object. (C:\Users\stian\Source\Repos\minside\src\MinSide.Web\Areas\ClientApp\node_modules\mini-css-extract-plugin\dist\index.js:26:44)</p>
  </blockquote>
  
  <p>I have been following the update guide <a href="https://update.angular.io/" rel="noreferrer">https://update.angular.io/</a></p>
  
  <p>It looks like it is webpack related, but if anyone know how to fix this or has experienced it themselves. Help is appreciated</p>