Card Widget Deprecation Notices

[joeparsons]

Problem/Motivation

The card widget currently generates PHP deprecation notices when previewing cards which have no link uri.

Describe the bug

Deprecated function: str_starts_with(): Passing null to parameter #1 ($haystack) of type string is deprecated in Drupal\az_card\Plugin\Field\FieldWidget\AZCardWidget->formElement() (line 173 of /src/az-quickstart-scaffolding/web/profiles/custom/az_quickstart/modules/custom/az_card/src/Plugin/Field/FieldWidget/AZCardWidget.php)
#0 /src/az-quickstart-scaffolding/web/core/includes/bootstrap.inc(166): _drupal_error_handler_real()
#1 [internal function]: _drupal_error_handler()
#2 /src/az-quickstart-scaffolding/web/profiles/custom/az_quickstart/modules/custom/az_card/src/Plugin/Field/FieldWidget/AZCardWidget.php(173): str_starts_with()
#3 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Field/WidgetBase.php(459): Drupal\az_card\Plugin\Field\FieldWidget\AZCardWidget->formElement()
#4 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Field/WidgetBase.php(219): Drupal\Core\Field\WidgetBase->formSingleElement()
#5 /src/az-quickstart-scaffolding/web/profiles/custom/az_quickstart/modules/custom/az_card/src/Plugin/Field/FieldWidget/AZCardWidget.php(339): Drupal\Core\Field\WidgetBase->formMultipleElements()
#6 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Field/WidgetBase.php(120): Drupal\az_card\Plugin\Field\FieldWidget\AZCardWidget->formMultipleElements()
#7 /src/az-quickstart-scaffolding/web/profiles/custom/az_quickstart/modules/custom/az_card/src/Plugin/Field/FieldWidget/AZCardWidget.php(95): Drupal\Core\Field\WidgetBase->form()
#8 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Entity/Entity/EntityFormDisplay.php(190): Drupal\az_card\Plugin\Field\FieldWidget\AZCardWidget->form()
#9 /src/az-quickstart-scaffolding/web/modules/contrib/paragraphs/src/Plugin/Field/FieldWidget/ParagraphsWidget.php(835): Drupal\Core\Entity\Entity\EntityFormDisplay->buildForm()
#10 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Field/WidgetBase.php(459): Drupal\paragraphs\Plugin\Field\FieldWidget\ParagraphsWidget->formElement()
#11 /src/az-quickstart-scaffolding/web/modules/contrib/paragraphs/src/Plugin/Field/FieldWidget/ParagraphsWidget.php(1381): Drupal\Core\Field\WidgetBase->formSingleElement()
#12 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Field/WidgetBase.php(120): Drupal\paragraphs\Plugin\Field\FieldWidget\ParagraphsWidget->formMultipleElements()
#13 /src/az-quickstart-scaffolding/web/modules/contrib/paragraphs/src/Plugin/Field/FieldWidget/ParagraphsWidget.php(1503): Drupal\Core\Field\WidgetBase->form()
#14 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Entity/Entity/EntityFormDisplay.php(190): Drupal\paragraphs\Plugin\Field\FieldWidget\ParagraphsWidget->form()
#15 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Entity/ContentEntityForm.php(121): Drupal\Core\Entity\Entity\EntityFormDisplay->buildForm()
#16 /src/az-quickstart-scaffolding/web/core/modules/node/src/NodeForm.php(134): Drupal\Core\Entity\ContentEntityForm->form()
#17 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Entity/EntityForm.php(107): Drupal\node\NodeForm->form()
#18 [internal function]: Drupal\Core\Entity\EntityForm->buildForm()
#19 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Form/FormBuilder.php(536): call_user_func_array()
#20 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Form/FormBuilder.php(375): Drupal\Core\Form\FormBuilder->retrieveForm()
#21 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Form/FormBuilder.php(633): Drupal\Core\Form\FormBuilder->rebuildForm()
#22 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Form/FormBuilder.php(326): Drupal\Core\Form\FormBuilder->processForm()
#23 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Controller/FormController.php(73): Drupal\Core\Form\FormBuilder->buildForm()
#24 [internal function]: Drupal\Core\Controller\FormController->getContentResult()
#25 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array()
#26 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/Render/Renderer.php(638): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#27 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(121): Drupal\Core\Render\Renderer->executeInRenderContext()
#28 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext()
#29 /src/az-quickstart-scaffolding/vendor/symfony/http-kernel/HttpKernel.php(181): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#30 /src/az-quickstart-scaffolding/vendor/symfony/http-kernel/HttpKernel.php(76): Symfony\Component\HttpKernel\HttpKernel->handleRaw()
#31 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/StackMiddleware/Session.php(53): Symfony\Component\HttpKernel\HttpKernel->handle()
#32 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle()
#33 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/StackMiddleware/ContentLength.php(28): Drupal\Core\StackMiddleware\KernelPreHandle->handle()
#34 /src/az-quickstart-scaffolding/web/core/modules/big_pipe/src/StackMiddleware/ContentLength.php(32): Drupal\Core\StackMiddleware\ContentLength->handle()
#35 /src/az-quickstart-scaffolding/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\big_pipe\StackMiddleware\ContentLength->handle()
#36 /src/az-quickstart-scaffolding/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass()
#37 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\page_cache\StackMiddleware\PageCache->handle()
#38 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()
#39 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/StackMiddleware/AjaxPageState.php(36): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()
#40 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/StackMiddleware/StackedHttpKernel.php(51): Drupal\Core\StackMiddleware\AjaxPageState->handle()
#41 /src/az-quickstart-scaffolding/web/core/lib/Drupal/Core/DrupalKernel.php(741): Drupal\Core\StackMiddleware\StackedHttpKernel->handle()
#42 /src/az-quickstart-scaffolding/web/index.php(19): Drupal\Core\DrupalKernel->handle()
#43 {main}

To Reproduce

• Create a card deck which contains a card which has no link URI.
• Save the page
• Edit the page
• Open the card deck and the associated card
• Close them, and repeat
• Check the Drupal watchdog log for PHP deprecation notices

Proposed resolution

The card widget should guard against using the link uri without checking its value first.

Expected behavior

Using the card widget should not generate PHP notices.