Symfony\Component\Routing\Exception\RouteNotFoundException

Drupal\Core\Routing\RouteProvider->getRouteByName(NULL)
Drupal\Core\Routing\UrlGenerator->getRoute(NULL)
Drupal\Core\Routing\UrlGenerator->generateFromRoute(NULL, [Array], [Array])
Drupal::url(NULL, [Array])
xmlsitemap_install()
call_user_func_array(xmlsitemap_install, [Array])
Drupal\Core\Extension\ModuleHandler->invoke(xmlsitemap, install)
Drupal\Core\Extension\ModuleInstaller->install([Array])
Drupal\system\Form\ModulesListForm->submitForm([Array], Drupal\Core\Form\FormState)
call_user_func_array([Array], [Array])
Drupal\Core\Form\FormSubmitter->executeSubmitHandlers([Array], Drupal\Core\Form\FormState)
Drupal\Core\Form\FormSubmitter->doSubmitForm([Array], Drupal\Core\Form\FormState)
Drupal\Core\Form\FormBuilder->processForm(system_modules, [Array], Drupal\Core\Form\FormState)
Drupal\Core\Form\FormBuilder->buildForm(Drupal\system\Form\ModulesListForm, Drupal\Core\Form\FormState)
Drupal\Core\Controller\FormController->getContentResult(Symfony\Component\HttpFoundation\Request)
call_user_func_array([Array], [Array])
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Symfony\Component\HttpFoundation\Request, 1)
Symfony\Component\HttpKernel\HttpKernel->handle(Symfony\Component\HttpFoundation\Request, 1, TRUE)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Symfony\Component\HttpFoundation\Request, 1, TRUE)
Drupal\Core\StackMiddleware\PageCache->handle(Symfony\Component\HttpFoundation\Request, 1, TRUE)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Symfony\Component\HttpFoundation\Request, 1, TRUE)
Stack\StackedHttpKernel->handle(Symfony\Component\HttpFoundation\Request, 1, TRUE)
Drupal\Core\DrupalKernel->handle(Symfony\Component\HttpFoundation\Request)