title: TypeError: Cannot read property 'components' of undefined in Vue2
body: <p>I'm using mixins in the subset components of app.vue without any problems, everything is good and works fine, but when I want to use it into the app.vue component, i'm having error in console.</p>
  
  <pre><code>&lt;script&gt;
  /* eslint-disable */
  import PanelUser from "./layouts/PanelUser";
  import Auth from "./mixins/Auth";
  export default {
    name: "App",
    mixins: [Auth],
    components: {
      PanelUser
    },
  };
  &lt;/script&gt;
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/HGg17.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HGg17.png" alt="error"></a></p>
  
  <p>I also can not use the router; when I use it, the page is completely white and nothing is displayed.</p>