Error message

• Notice: Undefined variable: host in avant_garde_preprocess_html() (line 23 of themes/custom/avant_garde/avant_garde.theme).

  avant_garde_preprocess_html(Array, 'html', Array) (Line: 287)
  Drupal\Core\Theme\ThemeManager->render('html', Array) (Line: 431)
  Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 200)
  Drupal\Core\Render\Renderer->render(Array) (Line: 147)
  Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 573)
  Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 148)
  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)
  

• Notice: Only variables should be passed by reference in avant_garde_preprocess_html() (line 25 of themes/custom/avant_garde/avant_garde.theme).

  avant_garde_preprocess_html(Array, 'html', Array) (Line: 287)
  Drupal\Core\Theme\ThemeManager->render('html', Array) (Line: 431)
  Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 200)
  Drupal\Core\Render\Renderer->render(Array) (Line: 147)
  Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 573)
  Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 148)
  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)