Can’t extend Ultimate theme login page

Step to reproduce. Following documentation https://www.laraship.com/docs/laraship/customize-laraship/customize-themes-using-theme-manager/ Theme.json:

{
  "type": "frontend",
  "name": "ultimatum",
  "extends": "corals-ecommerce-ultimate",
  "caption": "Ultimatum",
  "version": "1.0",
  "assetPath": "assets\/themes\/ultimatum"
}

Works fine so far. Now, for instance even copying the same auth/login.blade.php into the new theme. Visit: http://localhost/login and error is thrown. ErrorException (E_ERROR) Object of class Illuminate\Routing\UrlGenerator could not be converted to string (View: /home/vagrant/PUB/resources/themes/ecommerce-ultimate/layouts/auth.blade.php)

..

Symfony\Component\Debug\Exception\FatalThrowableError …/Corals/core/Theme/Themes.php 394 .  Thanks in advance