Problem/Motivation
When using the custom field linkit form widget on PHP 8.1 you get an error when saving the entity with the custom field. The problem is the $value['options']['attributes'] array is not set when trying to merge the $value['attributes'] in.
The error:
TypeError: Unsupported operand types: null + array in Drupal\custom_field_linkit\Plugin\CustomField\FieldWidget\LinkitWidget->massageFormValue() (line 202 of modules/contrib/custom_field/modules/custom_field_linkit/src/Plugin/CustomField/FieldWidget/LinkitWidget.php).
Drupal\custom_field\Plugin\Field\FieldWidget\CustomWidgetBase->massageFormValues(Array, Array, Object) (Line: 513)
Drupal\Core\Field\WidgetBase->extractFormValues(Object, Array, Object) (Line: 256)
Drupal\Core\Entity\Entity\EntityFormDisplay->extractFormValues(Object, Array, Object) (Line: 334)
Drupal\Core\Entity\ContentEntityForm->copyFormValuesToEntity(Object, Array, Object) (Line: 301)
Drupal\Core\Entity\EntityForm->buildEntity(Array, Object) (Line: 155)
Drupal\Core\Entity\ContentEntityForm->buildEntity(Array, Object) (Line: 186)
Drupal\Core\Entity\ContentEntityForm->validateForm(Array, Object)
call_user_func_array(Array, Array) (Line: 82)
Drupal\Core\Form\FormValidator->executeValidateHandlers(Array, Object) (Line: 275)
Drupal\Core\Form\FormValidator->doValidateForm(Array, Object, 'node_product_edit_form') (Line: 118)
Drupal\Core\Form\FormValidator->validateForm('node_product_edit_form', Array, Object) (Line: 585)
Drupal\Core\Form\FormBuilder->processForm('node_product_edit_form', Array, Object) (Line: 321)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->{closure:Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber::wrapControllerExecutionInRenderContext():121}() (Line: 627)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 121)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->{closure:Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber::onController():96}() (Line: 183)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 53)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle(Object, 1, 1) (Line: 263)
Drupal\shield\ShieldMiddleware->bypass(Object, 1, 1) (Line: 171)
Drupal\shield\ShieldMiddleware->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 53)
Drupal\Core\StackMiddleware\AjaxPageState->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object, 1, 1) (Line: 715)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)Proposed resolution
Set the $value['options']['attributes'] to an empty array when it is not set.