Error message

Notice: Undefined offset: 0 in node_class_preprocess_node() (line 58 of modules/contrib/node_class/node_class.module).

node_class_preprocess_node(Array, 'node', Array) (Line: 287)
Drupal\Core\Theme\ThemeManager->render('node', Array) (Line: 431)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 200)
Drupal\Core\Render\Renderer->render(Array) (Line: 501)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 76)
__TwigTemplate_d24d7367cace216038d5f0ed75fc56061af03beda8e87933620afc2df5c78009->doDisplay(Array, Array) (Line: 455)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 422)
Twig\Template->display(Array) (Line: 434)
Twig\Template->render(Array) (Line: 64)
twig_render_template('core/modules/views/templates/views-view-unformatted.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('views_view_unformatted', Array) (Line: 431)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 444)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 200)
Drupal\Core\Render\Renderer->render(Array) (Line: 501)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 126)
__TwigTemplate_dfb1e4287c560a66327ac4e6aed19102b6cf5b804ad435d23d9ed454e076bf50->doDisplay(Array, Array) (Line: 455)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 422)
Twig\Template->display(Array) (Line: 434)
Twig\Template->render(Array) (Line: 64)
twig_render_template('themes/contrib/bootstrap/templates/views/views-view.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('views_view', Array) (Line: 431)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 444)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 200)
Drupal\Core\Render\Renderer->render(Array, ) (Line: 226)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 573)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 227)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 117)
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('kernel.view', Object) (Line: 156)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 68)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
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: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 708)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)