lbry.com/controller/action/NavActions.class.php

<?php

class NavActions extends Actions
{
  protected static $navUri;

  public static function setNavUri($uri)
  {
    static::$navUri = $uri;
  }

  public static function getNavUri()
  {
    return static::$navUri ?: Request::getRelativeUri();
  }

  public static function prepareFooterPartial(array $vars)
  {
    return $vars + [
      'showLearnFooter' => false
    ];
  }

  public static function prepareGlobalItemsPartial(array $vars)
  {
    return $vars += [
      'selectedItem' => static::getNavUri(),
      'selectedCulture' => i18n::getLanguage() . '_' . i18n::getCountry(),
      'cultures' => i18n::getAllCultures()
    ];
  }

  public static function execute400(array $vars)
  {
    Response::setStatus(400);
    return ['page/400', ['error' => $vars['error'] ?? null]];
  }

  public static function execute404()
  {
//    $uri = Request::getRelativeUri();
//    Controller::queueToRunAfterResponse(function() use($uri) {
//      Slack::sendErrorIfProd('404 for url ' . $uri, false);
//    });
    Response::setStatus(404);
    return ['page/404'];
  }
}