facet_source_id: null - Facets not currently associated with any facet source

Problem/Motivation

Using the latest 3.0.x-dev facets version, all my facets don't have a facet_source_id anymore.

Trying to edit one of these "broken" / unassigned facets, e.g. /admin/config/search/facets/topic/edit
gives me:

Error: Call to a member function getDataDefinition() on null in Drupal\facets\Entity\Facet->getDataDefinition() (line 638 of modules/contrib/facets/src/Entity/Facet.php).

Drupal\facets\Plugin\facets\processor\BooleanItemProcessor->supportsFacet() (Line: 242)
Drupal\facets\Form\FacetForm->form() (Line: 107)
Drupal\Core\Entity\EntityForm->buildForm()
call_user_func_array() (Line: 536)
Drupal\Core\Form\FormBuilder->retrieveForm() (Line: 284)
Drupal\Core\Form\FormBuilder->buildForm() (Line: 73)
Drupal\Core\Controller\FormController->getContentResult() (Line: 39)
Drupal\layout_builder\Controller\LayoutBuilderHtmlEntityFormController->getContentResult()
call_user_func_array() (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 638)
Drupal\Core\Render\Renderer->executeInRenderContext() (Line: 121)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext() (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 181)
Symfony\Component\HttpKernel\HttpKernel->handleRaw() (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 53)
Drupal\Core\StackMiddleware\Session->handle() (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle() (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle() (Line: 50)
Drupal\ban\BanMiddleware->handle() (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle() (Line: 49)
Drupal\remove_http_headers\StackMiddleware\RemoveHttpHeadersMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle() (Line: 741)
Drupal\Core\DrupalKernel->handle() (Line: 19)

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes