Vue template or render function not defined yet I am using neither?

In my case, I was getting the error because I upgraded from Laravel Mix Version 2 to 5.

In Laravel Mix Version 2, you import vue components as follows:

Vue.component(
    'example-component', 
    require('./components/ExampleComponent.vue')
);

In Laravel Mix Version 5, you have to import your components as follows:

import ExampleComponent from './components/ExampleComponent.vue';

Vue.component('example-component', ExampleComponent);

Here is the documentation: https://laravel-mix.com/docs/5.0/upgrade

Better, to improve performance of your app, you can lazy load your components as follows:

Vue.component("ExampleComponent", () => import("./components/ExampleComponent"));