Regression: Missing entities in renamed relationships cause error 500

Problem/Motivation

JSON:API responds with a 500 error on the resource list when a referenced entity is deleted without removing the reference from the resource.

Steps to reproduce with a default Drupal 8.6.10, JSON:API 2.3 and JSON:API Extras 3.4 installation (latest):
- Have a content type, e.g. Article with a taxonomy reference field, e.g. field_tag referencing Tag taxonomy terms
- Overwrite JSON:API settings and change the alias of field_tag to something else, e.g. field_tag_alias
- Create an Article and choose a Tag
- Delete the Tag taxonomy term that is referenced, but do not remove it from the Article
- Visit /jsonapi/node/article and get a 500 error with the following message

Error: Call to a member function getTypeName() on boolean in Drupal\jsonapi\JsonApiResource\ResourceIdentifier->__construct() (line 79 of modules/contrib/jsonapi/src/JsonApiResource/ResourceIdentifier.php).

Drupal\jsonapi\JsonApiResource\ResourceIdentifier->__construct(, 'missing', Array) (Line: 450)
Drupal\jsonapi\JsonApiResource\ResourceIdentifier::getVirtualOrMissingResourceIdentifier(Object) (Line: 282)
Drupal\jsonapi\JsonApiResource\ResourceIdentifier::toResourceIdentifier(Object) (Line: 315)
Drupal\jsonapi\JsonApiResource\ResourceIdentifier::toResourceIdentifiers(Object) (Line: 52)
Drupal\jsonapi\Normalizer\EntityReferenceFieldNormalizer->normalize(Object, 'api_json', Array) (Line: 143)
Symfony\Component\Serializer\Serializer->normalize(Object, 'api_json', Array) (Line: 58)
Drupal\jsonapi\Serializer\Serializer->normalize(Object, 'api_json', Array)
call_user_func_array(Array, Array) (Line: 67)
Drupal\jsonapi_extras\SerializerDecorator->relay('normalize', Array) (Line: 102)
Drupal\jsonapi_extras\SerializerDecorator->normalize(Object, 'api_json', Array) (Line: 95)
Drupal\jsonapi\Normalizer\ResourceObjectNormalizer->serializeField(Object, Array, 'api_json') (Line: 55)
Drupal\jsonapi\Normalizer\ResourceObjectNormalizer->normalize(Object, 'api_json', Array) (Line: 37)
Drupal\jsonapi_extras\Normalizer\ResourceObjectNormalizer->normalize(Object, 'api_json', Array) (Line: 143)
Symfony\Component\Serializer\Serializer->normalize(Object, 'api_json', Array) (Line: 61)
Drupal\jsonapi\Serializer\Serializer->normalize(Object, 'api_json', Array) (Line: 253)
Drupal\jsonapi\Normalizer\JsonApiDocumentTopLevelNormalizer->Drupal\jsonapi\Normalizer\{closure}(Object)
array_map(Object, Array) (Line: 254)
Drupal\jsonapi\Normalizer\JsonApiDocumentTopLevelNormalizer->normalizeEntityCollection(Object, 'api_json', Array) (Line: 182)
Drupal\jsonapi\Normalizer\JsonApiDocumentTopLevelNormalizer->normalize(Object, 'api_json', Array) (Line: 143)
Symfony\Component\Serializer\Serializer->normalize(Object, 'api_json', Array) (Line: 58)
Drupal\jsonapi\Serializer\Serializer->normalize(Object, 'api_json', Array)
call_user_func_array(Array, Array) (Line: 67)
Drupal\jsonapi_extras\SerializerDecorator->relay('normalize', Array) (Line: 102)
Drupal\jsonapi_extras\SerializerDecorator->normalize(Object, 'api_json', Array) (Line: 115)
Drupal\jsonapi\EventSubscriber\ResourceResponseSubscriber->renderResponseBody(Object, Object, Object, 'api_json') (Line: 80)
Drupal\jsonapi\EventSubscriber\ResourceResponseSubscriber->onResponse(Object, 'kernel.response', Object)
call_user_func(Array, Object, 'kernel.response', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('kernel.response', Object) (Line: 191)
Symfony\Component\HttpKernel\HttpKernel->filterResponse(Object, Object, 1) (Line: 173)
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: 41)
Drupal\jsonapi\StackMiddleware\FormatSetter->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: 693)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Proposed resolution

I think it has something to do with \Drupal\jsonapi\ResourceType\ResourceType::getRelatableResourceTypesByField() not being overriden in \Drupal\jsonapi_extras\ResourceType\ConfigurableResourceType.

Remaining tasks

Discussion, Patch, etc.

User interface changes

None expected.

API changes

None expected.

Data model changes

None expected.

Release notes snippet

None expected.