TypeError: EntityListBuilder::getOperations(): Argument #1 must be of type EntityInterface

Problem/Motivation

Linked with #3511997: Allow deleting Content Template entity without deleting source Node, upon deleting a Content Template at /admin/content/template, I get the following error:

The website encountered an unexpected error. Try again later.

TypeError: Drupal\Core\Entity\EntityListBuilder::getOperations(): Argument #1 ($entity) must be of type Drupal\Core\Entity\EntityInterface, null given, called in /app/web/modules/contrib/content_templates/src/ContentTemplateListBuilder.php on line 47 in Drupal\Core\Entity\EntityListBuilder->getOperations() (line 131 of core/lib/Drupal/Core/Entity/EntityListBuilder.php).
Drupal\content_templates\ContentTemplateListBuilder->getOperations(Object) (Line: 242)
Drupal\Core\Entity\EntityListBuilder->buildOperations(Object) (Line: 224)
Drupal\Core\Entity\EntityListBuilder->buildRow(Object) (Line: 39)
Drupal\content_templates\ContentTemplateListBuilder->buildRow(Object) (Line: 272)
Drupal\Core\Entity\EntityListBuilder->render() (Line: 23)
Drupal\Core\Entity\Controller\EntityListController->listing('content_template')
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 593)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 121)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 183)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 54)
Drupal\simple_oauth\HttpMiddleware\BasicAuthSwap->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: 116)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 90)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 53)
Asm89\Stack\Cors->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: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object, 1, 1) (Line: 709)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Steps to reproduce

1. Set a Node as a Content Template
2. Remove the Content Template in the UI

Proposed resolution

Implement better null handling, especially after the delete action if no other Content Templates remain.

Remaining tasks

Fix, review and test.

User interface changes

N/A

API changes

N/A

Data model changes

N/A