Error if use with layout builder

Problem/Motivation

I'm testing the module and it seems very good to me, it meets what I need but I was doing tests to use it in the layout builder but I see that it gives me this problem

The website encountered an unexpected error. Try again later.
TypeError: strlen(): Argument #1 ($string) must be of type string, array given in strlen() (line 395 of core/lib/Drupal/Component/Utility/Unicode.php).
Drupal\Component\Utility\Unicode::validateUtf8() (Line: 65)
Drupal\Component\Utility\Xss::filter() (Line: 398)
Drupal\toc_ng\Plugin\Block\TocNgBlock->buildToc() (Line: 435)
Drupal\toc_ng\Plugin\Block\TocNgBlock->build() (Line: 106)
Drupal\layout_builder\EventSubscriber\BlockComponentRenderArray->onBuildRender()
call_user_func() (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch() (Line: 90)
Drupal\layout_builder\SectionComponent->toRenderArray() (Line: 88)
Drupal\layout_builder\Section->toRenderArray() (Line: 228)
Drupal\layout_builder\Element\LayoutBuilder->buildAdministrativeSection() (Line: 112)
Drupal\layout_builder\Element\LayoutBuilder->layout() (Line: 86)
Drupal\layout_builder\Element\LayoutBuilder->preRender()
call_user_func_array() (Line: 111)
Drupal\Core\Render\Renderer->doTrustedCallback() (Line: 859)
Drupal\Core\Render\Renderer->doCallback() (Line: 421)
Drupal\Core\Render\Renderer->doRender() (Line: 493)
Drupal\Core\Render\Renderer->doRender() (Line: 240)
Drupal\Core\Render\Renderer->render() (Line: 238)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 627)
Drupal\Core\Render\Renderer->executeInRenderContext() (Line: 239)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare() (Line: 128)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse() (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray()
call_user_func() (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch() (Line: 186)
Symfony\Component\HttpKernel\HttpKernel->handleRaw() (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 58)
Drupal\Core\StackMiddleware\Session->handle() (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle() (Line: 32)
Drupal\big_pipe\StackMiddleware\ContentLength->handle() (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle() (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle() (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle() (Line: 704)
Drupal\Core\DrupalKernel->handle() (Line: 19)

Steps to reproduce

- create a content type
- activate layout builder and use toc ng block

with that reproduce the error