v4 examples, empty navbars.

Created by: gpakosz

Despite #17532 (closed) being marked as resolved and closed, visiting https://v4-alpha.getbootstrap.com/examples/navbar-top-fixed/ gives a navbar containing nothing but the toggler:

    <div class="pos-f-t">
      <div class="collapse" id="navbar-header">
        <div class="container-fluid bg-inverse p-1">
          <h3>Collapsed content</h3>
          <p>Toggleable via the navbar brand.</p>
        </div>
      </div>
      <div class="navbar navbar-light bg-faded navbar-static-top">
        <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbar-header" aria-controls="navbar-header" aria-expanded="false" aria-label="Toggle navigation"></button>
      </div>
    </div>

The parent documentation page features a screenshot of a navbar containing many different items but here is what I get: