public function getMediaUri()
    {
       $folder = $this->getMediaFolder();

       if (strpos($folder, '://')) {
           return $folder;
       }

       /** @var UniformResourceLocator $locator */
       $locator = Grav::instance()['locator'];
       $user = $locator->findResource('user://');
       if (strpos($folder, $user) === 0) {
           return 'user://' . substr($folder, \strlen($user)+1);
       }

       return null;
    }