Call to a member function delete()

Problem/Motivation

After install this module, when i want to remove menu item from my node i have got this error:

Error: Call to a member function delete() on null in menu_ui_form_node_form_submit() (line 374 of core/modules/menu_ui/menu_ui.module).

menu_ui_form_node_form_submit(Array, Object)
call_user_func_array('menu_ui_form_node_form_submit', Array) (Line: 111)
Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object) (Line: 51)
Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object) (Line: 585)
Drupal\Core\Form\FormBuilder->processForm('node_content_type_page_edit_form', Array, Object) (Line: 314)
Drupal\Core\Form\FormBuilder->buildForm('node_content_type_page_edit_form', Object) (Line: 74)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 574)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 135)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 57)
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: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 50)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 656)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Proposed resolution

I can see that menu_item_extras attach service "menu_item_extras.menu_link_content_helper" in line 309, which do the same like function menu_ui_form_node_form_submit() in core menu_ui module, but core do not check if $entity object is not null.

API changes

• Detach this services?
• Fix this issue