Error message

Warning: Undefined array key "" in Drupal\better_exposed_filters\BetterExposedFiltersHelper::sortNestedOptions() (line 186 of modules/contrib/better_exposed_filters/src/BetterExposedFiltersHelper.php).

Drupal\better_exposed_filters\BetterExposedFiltersHelper::sortNestedOptions(Array, '-') (Line: 316)
Drupal\better_exposed_filters\Plugin\better_exposed_filters\filter\FilterWidgetBase->processSortedOptions(Array, Object, Array)
call_user_func_array(Array, Array) (Line: 1012)
Drupal\Core\Form\FormBuilder->doBuildForm('views_exposed_form', Array, Object) (Line: 1075)
Drupal\Core\Form\FormBuilder->doBuildForm('views_exposed_form', Array, Object) (Line: 579)
Drupal\Core\Form\FormBuilder->processForm('views_exposed_form', Array, Object) (Line: 325)
Drupal\Core\Form\FormBuilder->buildForm('\Drupal\views\Form\ViewsExposedForm', Object) (Line: 134)
Drupal\views\Plugin\views\exposed_form\ExposedFormPluginBase->renderExposedForm() (Line: 1253)
Drupal\views\ViewExecutable->build(NULL) (Line: 1406)
Drupal\views\ViewExecutable->execute() (Line: 167)
Drupal\viewfield\Plugin\Field\FieldFormatter\ViewfieldFormatterDefault->viewElements(Object, 'en') (Line: 89)
Drupal\Core\Field\FormatterBase->view(Object, 'en') (Line: 96)
Drupal\viewfield\Plugin\Field\FieldFormatter\ViewfieldFormatterDefault->view(Object, NULL) (Line: 265)
Drupal\Core\Entity\Entity\EntityViewDisplay->buildMultiple(Array) (Line: 266)
Drupal\layout_builder\Entity\LayoutBuilderEntityViewDisplay->buildMultiple(Array) (Line: 339)
Drupal\Core\Entity\EntityViewBuilder->buildComponents(Array, Array, Array, 'default') (Line: 281)
Drupal\Core\Entity\EntityViewBuilder->buildMultiple(Array) (Line: 18)
Drupal\paragraphs\ParagraphViewBuilder->buildMultiple(Array) (Line: 238)
Drupal\Core\Entity\EntityViewBuilder->build(Array)
call_user_func_array(Array, Array) (Line: 101)
Drupal\Core\Render\Renderer->doTrustedCallback(Array, Array, 'Render #pre_render callbacks must be methods of a class that implements \Drupal\Core\Security\TrustedCallbackInterface or be an anonymous function. The callback was %s. See https://www.drupal.org/node/2966725', 'exception', 'Drupal\Core\Render\Element\RenderCallbackInterface') (Line: 788)
Drupal\Core\Render\Renderer->doCallback('#pre_render', Array, Array) (Line: 374)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 204)
Drupal\Core\Render\Renderer->render(Array) (Line: 477)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 67)
__TwigTemplate_78ab5ab00f0184781c5b798fa411b64f->doDisplay(Array, Array) (Line: 394)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 367)
Twig\Template->display(Array) (Line: 379)
Twig\Template->render(Array, Array) (Line: 40)
Twig\TemplateWrapper->render(Array) (Line: 53)
twig_render_template('themes/contrib/bootstrap/templates/field/field.html.twig', Array) (Line: 372)
Drupal\Core\Theme\ThemeManager->render('field', Array) (Line: 433)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 204)
Drupal\Core\Render\Renderer->render(Array) (Line: 477)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 96)
__TwigTemplate_b0757fad221ebaf7b2a8f2e7ce32b2f1->doDisplay(Array, Array) (Line: 394)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 367)
Twig\Template->display(Array) (Line: 379)
Twig\Template->render(Array, Array) (Line: 40)
Twig\TemplateWrapper->render(Array) (Line: 53)
twig_render_template('themes/custom/nova/templates/node/node--969.html.twig', Array) (Line: 372)
Drupal\Core\Theme\ThemeManager->render('node', Array) (Line: 433)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 204)
Drupal\Core\Render\Renderer->render(Array, ) (Line: 238)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 580)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 239)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 128)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object)
call_user_func(Array, Object, 'kernel.view', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch(Object, 'kernel.view') (Line: 168)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 74)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 191)
Drupal\page_cache\StackMiddleware\PageCache->fetch(Object, 1, 1) (Line: 128)
Drupal\page_cache\StackMiddleware\PageCache->lookup(Object, 1, 1) (Line: 82)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object, 1, 1) (Line: 692)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)