pages_controller_decorator.rb

# /app/decorators/controllers/refinery/pages/pages_controller_decorator.rb
Refinery::PagesController.class_eval do

  def show
    if current_user_can_view_page?
      if should_skip_to_first_child?
        redirect_to refinery.url_for(first_live_child.url)
      elsif page.link_url.present? && redirect_url?
        redirect_to page.link_url
      else
        if requested_friendly_id != page.friendly_id && redirect_url?
          redirect_to refinery.url_for(page.url), :status => 301
        else
          render_with_templates?
        end
      end
    else
      error_404
    end
  end

  def redirect_url?
    page.link_url[0] == "/"
  end

  def find_page(fallback_to_404 = true)
    @page ||= case action_name
              when "home"
                Refinery::Page.where(:link_url => '/').first
              when "show"
                Refinery::Page.find_by_path_or_id(params[:path], params[:id]) || Refinery::Page.where(:link_url => "#{params[:path]}").first
              end
    @page || (error_404 if fallback_to_404)
  end

end

If link_url is nil you'll get the following:

nil[0]
NoMethodError: undefined method `[]' on nil:NilClass.

Why not just put the page.link_url.present? check inside redirect_url?