Fatal error when accessing global metatag config

#2563639: Global configuration via config entities introduced a global config system. However, when you actually try to access it at admin/structure/metatag_defaults, you get this fatal error:

The website encountered an unexpected error. Please try again later.
Recoverable fatal error: Argument 1 passed to Drupal\metatag\MetatagDefaultsListBuilder::buildRow() must implement interface Drupal\Core\Entity\EntityInterface, null given, called in core/lib/Drupal/Core/Entity/EntityListBuilder.php on line 234 and defined in Drupal\metatag\MetatagDefaultsListBuilder->buildRow() (line 39 of modules/contrib/metatag/src/MetatagDefaultsListBuilder.php).

Drupal\metatag\MetatagDefaultsListBuilder->buildRow(NULL)
Drupal\Core\Entity\EntityListBuilder->render()
Drupal\metatag\MetatagDefaultsListBuilder->render()
Drupal\Core\Entity\Controller\EntityListController->listing('metatag_defaults')
call_user_func_array(Array, Array)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
call_user_func_array(Object, Array)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1)
Stack\StackedHttpKernel->handle(Object, 1, 1)
Drupal\Core\DrupalKernel->handle(Object)