title: Heroku adding 'undefined' to BASE_URL environment variable
body: <p>attempting to deploy a vuejs, express app to heroku. The app displays, but cannot access the api, because heroku seems to add 'undefined' in the middle of the base_url. Everything works locally as expected.</p>
  
  <p>Here is my heroku config var:
  <code>BASE_URL:    https://goore-todos.herokuapp.com/</code></p>
  
  <p>Here is the Vuejs component api request:</p>
  
  <pre><code>fetchTodo () {
    let uri = process.env.BASE_URL + '/api/all';
    axios.get(uri).then((response) =&gt; {
      this.todos = response.data;
    });
  },
  </code></pre>
  
  <p>As mentioned, this works locally.</p>
  
  <p>the console shows the following error: 
      VM71:1 GET <a href="https://goore-todos.herokuapp.com/undefined/api/all" rel="nofollow noreferrer">https://goore-todos.herokuapp.com/undefined/api/all</a> 404 (Not Found)</p>
  
  <p>and the view is empty.</p>
  
  <p>requests to <a href="https://goore-todos.herokuapp.com/api/" rel="nofollow noreferrer">https://goore-todos.herokuapp.com/api/</a> via Postman work as expected.</p>