When entity is deleted TypeError is thrown

We're using the flag module as a favorite function. We use AJAX type flags. When a entity gets deleted and then a flag is still added, it will throw a fatal TypeError (see below). Of course, the entity shouldn't be flagged in the first place, but is still possible for people that are:

1. Seeing a entity on a page that they loaded before it was deleted.
2. Seeing a entity that is somehow still on a page due to caching. (this is rather poor caching then a flagging problem, but still)

TypeError: Argument 2 passed to Drupal\flag\FlagService::flag() must implement interface Drupal\Core\Entity\EntityInterface, null given, called in /my/project/web/modules/contrib/flag/src/Controller/ActionLinkController.php on line 77 in Drupal\flag\FlagService->flag() (line 252 of modules/contrib/flag/src/FlagService.php).
Drupal\flag\FlagService->flag(Object, NULL) (Line: 77)
Drupal\flag\Controller\ActionLinkController->flag(Object, '436', Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 582)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 151)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 68)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 666)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)