Error after login into the backend

[frontendschlampe]

PHP 8, Contao 4.13.4

TypeError:
sprintf(): Argument #1 ($format) must be of type string, null given

  at vendor/terminal42/contao-easy_themes/src/Helper.php:128
  at sprintf(null, 1)
     (vendor/terminal42/contao-easy_themes/src/Helper.php:128)
  at Terminal42\EasyThemesBundle\Helper->prepareBackendNavigationArray()
     (vendor/terminal42/contao-easy_themes/src/EventListener/UserNavigationListener.php:43)
  at Terminal42\EasyThemesBundle\EventListener\UserNavigationListener->__invoke(array('content' => array('class' => 'group-content node-expanded', 'title' => 'Bereich schließen', 'label' => 'Inhalte', 'href' => …
     (vendor/contao/core-bundle/src/Resources/contao/classes/BackendUser.php:560)
  at Contao\BackendUser->navigation()
     (vendor/contao/core-bundle/src/EventListener/Menu/BackendMenuListener.php:66)
  at Contao\CoreBundle\EventListener\Menu\BackendMenuListener->buildMainMenu(object(MenuEvent), object(BackendUser))
     (vendor/contao/core-bundle/src/EventListener/Menu/BackendMenuListener.php:56)
  at Contao\CoreBundle\EventListener\Menu\BackendMenuListener->__invoke(object(MenuEvent), 'contao.backend_menu_build', object(TraceableEventDispatcher))
     (vendor/symfony/event-dispatcher/Debug/WrappedListener.php:117)
  at Symfony\Component\EventDispatcher\Debug\WrappedListener->__invoke(object(MenuEvent), 'contao.backend_menu_build', object(TraceableEventDispatcher))
     (vendor/symfony/event-dispatcher/EventDispatcher.php:230)
  at Symfony\Component\EventDispatcher\EventDispatcher->callListeners(array(object(WrappedListener), object(WrappedListener), object(WrappedListener), object(WrappedListener)), 'contao.backend_menu_build', object(MenuEvent))
     (vendor/symfony/event-dispatcher/EventDispatcher.php:59)
  at Symfony\Component\EventDispatcher\EventDispatcher->dispatch(object(MenuEvent), 'contao.backend_menu_build')
     (vendor/symfony/event-dispatcher/Debug/TraceableEventDispatcher.php:154)
  at Symfony\Component\EventDispatcher\Debug\TraceableEventDispatcher->dispatch(object(MenuEvent), 'contao.backend_menu_build')
     (vendor/contao/core-bundle/src/Menu/BackendMenuBuilder.php:42)
  at Contao\CoreBundle\Menu\BackendMenuBuilder->buildMainMenu(array())
     (vendor/knplabs/knp-menu/src/Knp/Menu/Provider/LazyProvider.php:45)
  at Knp\Menu\Provider\LazyProvider->get('be_menu', array())
     (vendor/knplabs/knp-menu/src/Knp/Menu/Provider/ChainProvider.php:26)
  at Knp\Menu\Provider\ChainProvider->get('be_menu', array())
     (vendor/knplabs/knp-menu/src/Knp/Menu/Twig/Helper.php:67)
  at Knp\Menu\Twig\Helper->get('be_menu', array())
     (vendor/knplabs/knp-menu/src/Knp/Menu/Twig/Helper.php:164)
  at Knp\Menu\Twig\Helper->castMenu('be_menu')
     (vendor/knplabs/knp-menu/src/Knp/Menu/Twig/Helper.php:99)
  at Knp\Menu\Twig\Helper->render('be_menu', array(), null)
     (vendor/knplabs/knp-menu/src/Knp/Menu/Twig/MenuExtension.php:91)
  at Knp\Menu\Twig\MenuExtension->render('be_menu')
     (var/cache/dev/twig/30/300562a3eb40f85af0e1ad3325ae924d.php:54)
  at __TwigTemplate_0c75d7b382962d2da9f24845879670ef->doDisplay(array('app' => object(AppVariable)), array())
     (vendor/twig/twig/src/Template.php:394)
  at Twig\Template->displayWithErrorHandling(array('app' => object(AppVariable)), array())
     (vendor/twig/twig/src/Template.php:367)
  at Twig\Template->display(array())
     (vendor/twig/twig/src/Template.php:379)
  at Twig\Template->render(array(), array())
     (vendor/twig/twig/src/TemplateWrapper.php:40)
  at Twig\TemplateWrapper->render(array())
     (vendor/twig/twig/src/Environment.php:277)
  at Twig\Environment->render('@ContaoCore/Backend/be_menu.html.twig')
    (vendor/contao/core-bundle/src/Resources/contao/controllers/BackendMain.php:264)
  at Contao\BackendMain->compileTemplateData(array('version' => 'Version 4.13.4', …
     (vendor/contao/core-bundle/src/Resources/contao/controllers/BackendMain.php:220)
  at Contao\BackendMain->output()
     (vendor/contao/core-bundle/src/Resources/contao/controllers/BackendMain.php:172)
  at Contao\BackendMain->run()
     (vendor/contao/core-bundle/src/Controller/BackendController.php:49)
  at Contao\CoreBundle\Controller\BackendController->mainAction()
     (vendor/symfony/http-kernel/HttpKernel.php:152)
  at Symfony\Component\HttpKernel\HttpKernel->handleRaw(object(Request), 1)
     (vendor/symfony/http-kernel/HttpKernel.php:74)
  at Symfony\Component\HttpKernel\HttpKernel->handle(object(Request), 1, true)
     (vendor/symfony/http-kernel/Kernel.php:202)
  at Symfony\Component\HttpKernel\Kernel->handle(object(Request))
     (public/index.php:44)

[frontendschlampe]

local caching problem