Error: Call to a member function getEditable() on null in Drupal\wisski_core\Form\WisskiIndividualListConfirmFormDeleteAll->buildForm()

On which WissKI instance happened the incidence?

Default Data Model Cloud Instance

When does the issue occur?

When trying to delete (all) Entities of any Bundle, whether by clicking the "Delete all entities" button or selecting individual Entities and using the "Delete" button below.

On which page or in which action carried out?

Home > Administration > Structure > WissKI Bundles and Object Classes > [Bundle] > Individual List

What exactly lead to the behaviour?

Clicking on any button to delete Entities within the "Individual List" tab..

What did you expect? Do you want to display, configure or save something?

I expected to delete all the Entities.

What happened instead? Did the page crash, is there an error or did the action not take place?

I receives a white screen telling me that "The website encountered an unexpected error. Try again later." and found the following error in the logs:

#0 [internal function]: Drupal\wisski_core\Form\WisskiIndividualListConfirmFormDeleteAll->buildForm()
#1 /var/www/data/project/web/core/lib/Drupal/Core/Form/FormBuilder.php(528): call_user_func_array()
#2 /var/www/data/project/web/core/lib/Drupal/Core/Form/FormBuilder.php(279): Drupal\Core\Form\FormBuilder->retrieveForm()
#3 /var/www/data/project/web/core/lib/Drupal/Core/Controller/FormController.php(73): Drupal\Core\Form\FormBuilder->buildForm()
#4 [internal function]: Drupal\Core\Controller\FormController->getContentResult()
#5 /var/www/data/project/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array()
#6 /var/www/data/project/web/core/lib/Drupal/Core/Render/Renderer.php(627): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#7 /var/www/data/project/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(121): Drupal\Core\Render\Renderer->executeInRenderContext()
#8 /var/www/data/project/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext()
#9 /var/www/data/project/vendor/symfony/http-kernel/HttpKernel.php(183): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#10 /var/www/data/project/vendor/symfony/http-kernel/HttpKernel.php(76): Symfony\Component\HttpKernel\HttpKernel->handleRaw()
#11 /var/www/data/project/web/core/lib/Drupal/Core/StackMiddleware/Session.php(53): Symfony\Component\HttpKernel\HttpKernel->handle()
#12 /var/www/data/project/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle()
#13 /var/www/data/project/web/core/lib/Drupal/Core/StackMiddleware/ContentLength.php(28): Drupal\Core\StackMiddleware\KernelPreHandle->handle()
#14 /var/www/data/project/web/core/modules/big_pipe/src/StackMiddleware/ContentLength.php(32): Drupal\Core\StackMiddleware\ContentLength->handle()
#15 /var/www/data/project/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(116): Drupal\big_pipe\StackMiddleware\ContentLength->handle()
#16 /var/www/data/project/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(90): Drupal\page_cache\StackMiddleware\PageCache->pass()
#17 /var/www/data/project/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\page_cache\StackMiddleware\PageCache->handle()
#18 /var/www/data/project/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()
#19 /var/www/data/project/web/core/lib/Drupal/Core/StackMiddleware/AjaxPageState.php(53): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()
#20 /var/www/data/project/web/core/lib/Drupal/Core/StackMiddleware/StackedHttpKernel.php(51): Drupal\Core\StackMiddleware\AjaxPageState->handle()
#21 /var/www/data/project/web/core/lib/Drupal/Core/DrupalKernel.php(715): Drupal\Core\StackMiddleware\StackedHttpKernel->handle()
#22 /var/www/data/project/web/index.php(19): Drupal\Core\DrupalKernel->handle()
#23 {main}