Fix Cache Tags on node revision preview timestamp for a node content page

Reported by Razem

Step to reproduce

Go to any node / revision / click on a timestamp of a revision to preview it

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Error: Call to a member function id() on string in Drupal\varbase_media_header\Plugin\Block\VarbaseMediaHeaderBlock->getCacheTags() (line 220 of modules/contrib/varbase_media_header/src/Plugin/Block/VarbaseMediaHeaderBlock.php).
Drupal\varbase_media_header\Plugin\Block\VarbaseMediaHeaderBlock->getCacheTags() (Line: 47)
Drupal\block\BlockViewBuilder->viewMultiple(Array, 'full', NULL) (Line: 32)
Drupal\block\BlockViewBuilder->view(Object) (Line: 151)
Drupal\block\Plugin\DisplayVariant\BlockPageVariant->build() (Line: 259)
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: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
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: 694)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)