Warning: foreach() argument must be of type array|object, null given in Drupal\Core\Render\Element\Checkboxes::valueCallback() (line 113 of /core/lib/Drupal/Core/Render/Element/Checkboxes.ph

Problem/Motivation

With Drupal 9.4.4 and alinks 2.0.0, each installed by composer, freshly installed but not yet configured, the following warning was given on page /admin/config/content/alinks. Warning persists after cron run, cache flush, adding config options, etc.

Full log message:

Warning: foreach() argument must be of type array|object, null given in Drupal\Core\Render\Element\Checkboxes::valueCallback() (line 113 of /core/lib/Drupal/Core/Render/Element/Checkboxes.php)
#0 /core/includes/bootstrap.inc(347): _drupal_error_handler_real()
#1 /core/lib/Drupal/Core/Render/Element/Checkboxes.php(113): _drupal_error_handler()
#2 [internal function]: Drupal\Core\Render\Element\Checkboxes::valueCallback()
#3 /core/lib/Drupal/Core/Form/FormBuilder.php(1282): call_user_func_array()
#4 /core/lib/Drupal/Core/Form/FormBuilder.php(1000): Drupal\Core\Form\FormBuilder->handleInputElement()
#5 /core/lib/Drupal/Core/Form/FormBuilder.php(1070): Drupal\Core\Form\FormBuilder->doBuildForm()
#6 /core/lib/Drupal/Core/Form/FormBuilder.php(1070): Drupal\Core\Form\FormBuilder->doBuildForm()
#7 /core/lib/Drupal/Core/Form/FormBuilder.php(574): Drupal\Core\Form\FormBuilder->doBuildForm()
#8 /core/lib/Drupal/Core/Form/FormBuilder.php(320): Drupal\Core\Form\FormBuilder->processForm()
#9 /core/lib/Drupal/Core/Controller/FormController.php(73): Drupal\Core\Form\FormBuilder->buildForm()
#10 [internal function]: Drupal\Core\Controller\FormController->getContentResult()
#11 /core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array()
#12 /core/lib/Drupal/Core/Render/Renderer.php(564): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#13 /core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext()
#14 /core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext()
#15 /vendor/symfony/http-kernel/HttpKernel.php(158): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#16 /vendor/symfony/http-kernel/HttpKernel.php(80): Symfony\Component\HttpKernel\HttpKernel->handleRaw()
#17 /core/lib/Drupal/Core/StackMiddleware/Session.php(58): Symfony\Component\HttpKernel\HttpKernel->handle()
#18 /core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle()
#19 /core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\Core\StackMiddleware\KernelPreHandle->handle()
#20 /core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass()
#21 /core/modules/ban/src/BanMiddleware.php(50): Drupal\page_cache\StackMiddleware\PageCache->handle()
#22 /core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\ban\BanMiddleware->handle()
#23 /core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()
#24 /vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()
#25 /core/lib/Drupal/Core/DrupalKernel.php(709): Stack\StackedHttpKernel->handle()
#26 /index.php(19): Drupal\Core\DrupalKernel->handle()
#27 {main}