menu_ui_form_node_form_submit() is called when the Preview button is pressed which fatals

Problem/Motivation

Steps to reproduce

1. On a Standard installation go to Add content » Article and fill in a title
2. Click the Provide a menu link checkbox in the Menu settings details (in the sidebar).
3. Click Preview on the bottom of the page.

Expected result

You see a preview of the node (with or without a menu link).

Actual result

Drupal\Core\Entity\EntityStorageException: The entity URI "entity:node/" is invalid. You must specify the entity id in the URL. e.g., entity:node/1 for loading the canonical path to node entity with id 1. in Drupal\Core\Entity\Sql\SqlContentEntityStorage->save() (line 929 of core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php).
Drupal\Core\Url::fromUri('entity:node/')

• Drupal\link\Plugin\Field\FieldType\LinkItem->getUrl()
• Drupal\menu_link_content\Entity\MenuLinkContent->getUrlObject()
• Drupal\menu_link_content\Entity\MenuLinkContent->getPluginDefinition()
• Drupal\menu_link_content\Entity\MenuLinkContent->postSave(Object, )
• Drupal\Core\Entity\EntityStorageBase->save(Object)
• Drupal\Core\Entity\Sql\SqlContentEntityStorage->save(Object)
• Drupal\Core\Entity\Entity->save()
• _menu_ui_node_save(Object, Array)
• menu_ui_form_node_form_submit(Array, Object)
• call_user_func_array('menu_ui_form_node_form_submit', Array)
• Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object)
• Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object)
• Drupal\Core\Form\FormBuilder->processForm('node_article_form', Array, Object)
• Drupal\Core\Form\FormBuilder->buildForm(Object, Object)
• Drupal\Core\Entity\EntityFormBuilder->getForm(Object)
• Drupal\node\Controller\NodeController->add(Object)

...

Proposed resolution

Remaining tasks

User interface changes

API changes