Undefined index: field_event_all_day in social_event_form_alter()

This is happening on a node edit page, e.g. http://example.com/en/node/3738/edit

The line in question should be using isset(), but isn't:

    if ($form['field_event_all_day']['widget']['value']['#default_value']) {

This should be:

    if (isset($form['field_event_all_day']['widget']['value']['#default_value'])) {

Log entry:

Notice: Undefined index: field_event_all_day in social_event_form_alter() (line 671 of /app/web/profiles/contrib/social/modules/social_features/social_event/social_event.module)

#0 /app/web/core/includes/bootstrap.inc(312): _drupal_error_handler_real(8, 'Undefined index...', '/app/web/profil...', 671)
#1 /app/web/profiles/contrib/social/modules/social_features/social_event/social_event.module(671): _drupal_error_handler(8, 'Undefined index...', '/app/web/profil...', 671, Array)
#2 /app/web/core/lib/Drupal/Core/Extension/ModuleHandler.php(539): social_event_form_alter(Array, Object(Drupal\Core\Form\FormState), 'node_event_edit...')
#3 /app/web/core/lib/Drupal/Core/Form/FormBuilder.php(836): Drupal\Core\Extension\ModuleHandler->alter('form', Array, Object(Drupal\Core\Form\FormState), 'node_event_edit...')
#4 /app/web/core/lib/Drupal/Core/Form/FormBuilder.php(279): Drupal\Core\Form\FormBuilder->prepareForm('node_event_edit...', Array, Object(Drupal\Core\Form\FormState))
#5 /app/web/core/lib/Drupal/Core/Controller/FormController.php(73): Drupal\Core\Form\FormBuilder->buildForm(Object(Drupal\social_node\SocialNodeForm), Object(Drupal\Core\Form\FormState))
#6 [internal function]: Drupal\Core\Controller\FormController->getContentResult(Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\RouteMatch))
#7 /app/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array)
#8 /app/web/core/lib/Drupal/Core/Render/Renderer.php(578): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#9 /app/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure))
#10 /app/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array)
#11 /app/vendor/symfony/http-kernel/HttpKernel.php(158): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#12 /app/vendor/symfony/http-kernel/HttpKernel.php(80): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
#13 /app/web/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#14 /app/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#15 /app/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#16 /app/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(52): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#17 /app/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#18 /app/web/core/lib/Drupal/Core/DrupalKernel.php(717): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#19 /app/web/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))
#20 {main}