Exception in JSON:API fetching content.

Problem/Motivation

I am getting the following exception that results in 500 responses on the API rtesponses.
As this happens in production, it is not easy to debug at the moment...

Error: Call to a member function getTypeName() on null in Drupal\jsonapi\JsonApiResource\ResourceIdentifier->__construct() (line 83 of /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/JsonApiResource/ResourceIdentifier.php)
 #0 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/JsonApiResource/ResourceIdentifier.php(299): Drupal\jsonapi\JsonApiResource\ResourceIdentifier->__construct(NULL, '16200c62-496d-4...', Array)
 #1 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/JsonApiResource/ResourceIdentifier.php(319): Drupal\jsonapi\JsonApiResource\ResourceIdentifier::toResourceIdentifier(Object(Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem))
 #2 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/Normalizer/EntityReferenceFieldNormalizer.php(42): Drupal\jsonapi\JsonApiResource\ResourceIdentifier::toResourceIdentifiers(Object(Drupal\Core\Field\EntityReferenceFieldItemList))
 #3 /var/www/FOLDER/vendor/symfony/serializer/Serializer.php(143): Drupal\jsonapi\Normalizer\EntityReferenceFieldNormalizer->normalize(Object(Drupal\Core\Field\EntityReferenceFieldItemList), 'api_json', Array)
 #4 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/Serializer/Serializer.php(62): Symfony\Component\Serializer\Serializer->normalize(Object(Drupal\Core\Field\EntityReferenceFieldItemList), 'api_json', Array)
 #5 [internal function]: Drupal\jsonapi\Serializer\Serializer->normalize(Object(Drupal\Core\Field\EntityReferenceFieldItemList), 'api_json', Array)
 #6 /var/www/FOLDER/docroot/modules/contrib/jsonapi_extras/src/SerializerDecorator.php(67): call_user_func_array(Array, Array)
 #7 /var/www/FOLDER/docroot/modules/contrib/jsonapi_extras/src/SerializerDecorator.php(102): Drupal\jsonapi_extras\SerializerDecorator->relay('normalize', Array)
 #8 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/Normalizer/ResourceObjectNormalizer.php(93): Drupal\jsonapi_extras\SerializerDecorator->normalize(Object(Drupal\Core\Field\EntityReferenceFieldItemList), 'api_json', Array)
 #9 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/Normalizer/ResourceObjectNormalizer.php(59): Drupal\jsonapi\Normalizer\ResourceObjectNormalizer->serializeField(Object(Drupal\Core\Field\EntityReferenceFieldItemList), Array, 'api_json')
 #10 /var/www/FOLDER/docroot/modules/contrib/jsonapi_extras/src/Normalizer/ResourceObjectNormalizer.php(37): Drupal\jsonapi\Normalizer\ResourceObjectNormalizer->normalize(Object(Drupal\jsonapi\JsonApiResource\ResourceObject), 'api_json', Array)
 #11 /var/www/FOLDER/vendor/symfony/serializer/Serializer.php(143): Drupal\jsonapi_extras\Normalizer\ResourceObjectNormalizer->normalize(Object(Drupal\jsonapi\JsonApiResource\ResourceObject), 'api_json', Array)
 #12 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/Serializer/Serializer.php(65): Symfony\Component\Serializer\Serializer->normalize(Object(Drupal\jsonapi\JsonApiResource\ResourceObject), 'api_json', Array)
 #13 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/Normalizer/DataNormalizer.php(26): Drupal\jsonapi\Serializer\Serializer->normalize(Object(Drupal\jsonapi\JsonApiResource\ResourceObject), 'api_json', Array)
 #14 [internal function]: Drupal\jsonapi\Normalizer\DataNormalizer->Drupal\jsonapi\Normalizer\{closure}(Object(Drupal\jsonapi\JsonApiResource\ResourceObject))
 #15 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/Normalizer/DataNormalizer.php(27): array_map(Object(Closure), Array)
 #16 /var/www/FOLDER/vendor/symfony/serializer/Serializer.php(143): Drupal\jsonapi\Normalizer\DataNormalizer->normalize(Object(Drupal\jsonapi\JsonApiResource\IncludedData), 'api_json', Array)
 #17 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/Serializer/Serializer.php(62): Symfony\Component\Serializer\Serializer->normalize(Object(Drupal\jsonapi\JsonApiResource\IncludedData), 'api_json', Array)
 #18 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/Normalizer/JsonApiDocumentTopLevelNormalizer.php(201): Drupal\jsonapi\Serializer\Serializer->normalize(Object(Drupal\jsonapi\JsonApiResource\IncludedData), 'api_json', Array)
 #19 /var/www/FOLDER/vendor/symfony/serializer/Serializer.php(143): Drupal\jsonapi\Normalizer\JsonApiDocumentTopLevelNormalizer->normalize(Object(Drupal\jsonapi\JsonApiResource\JsonApiDocumentTopLevel), 'api_json', Array)
 #20 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/Serializer/Serializer.php(62): Symfony\Component\Serializer\Serializer->normalize(Object(Drupal\jsonapi\JsonApiResource\JsonApiDocumentTopLevel), 'api_json', Array)
 #21 [internal function]: Drupal\jsonapi\Serializer\Serializer->normalize(Object(Drupal\jsonapi\JsonApiResource\JsonApiDocumentTopLevel), 'api_json', Array)
 #22 /var/www/FOLDER/docroot/modules/contrib/jsonapi_extras/src/SerializerDecorator.php(67): call_user_func_array(Array, Array)
 #23 /var/www/FOLDER/docroot/modules/contrib/jsonapi_extras/src/SerializerDecorator.php(102): Drupal\jsonapi_extras\SerializerDecorator->relay('normalize', Array)
 #24 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/EventSubscriber/ResourceResponseSubscriber.php(120): Drupal\jsonapi_extras\SerializerDecorator->normalize(Object(Drupal\jsonapi\JsonApiResource\JsonApiDocumentTopLevel), 'api_json', Array)
 #25 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/EventSubscriber/ResourceResponseSubscriber.php(85): Drupal\jsonapi\EventSubscriber\ResourceResponseSubscriber->renderResponseBody(Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\jsonapi\ResourceResponse), Object(Drupal\jsonapi_extras\SerializerDecorator), 'api_json')
 #26 [internal function]: Drupal\jsonapi\EventSubscriber\ResourceResponseSubscriber->onResponse(Object(Symfony\Component\HttpKernel\Event\FilterResponseEvent), 'kernel.response', Object(Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher))
 #27 /var/www/FOLDER/docroot/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php(111): call_user_func(Array, Object(Symfony\Component\HttpKernel\Event\FilterResponseEvent), 'kernel.response', Object(Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher))
 #28 /var/www/FOLDER/vendor/symfony/http-kernel/HttpKernel.php(191): Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('kernel.response', Object(Symfony\Component\HttpKernel\Event\FilterResponseEvent))
 #29 /var/www/FOLDER/vendor/symfony/http-kernel/HttpKernel.php(173): Symfony\Component\HttpKernel\HttpKernel->filterResponse(Object(Drupal\jsonapi\ResourceResponse), Object(Symfony\Component\HttpFoundation\Request), 1)
 #30 /var/www/FOLDER/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
 #31 /var/www/FOLDER/docroot/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
 #32 /var/www/FOLDER/docroot/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
 #33 /var/www/FOLDER/docroot/modules/contrib/jsonapi/src/StackMiddleware/FormatSetter.php(45): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
 #34 /var/www/FOLDER/vendor/asm89/stack-cors/src/Asm89/Stack/Cors.php(49): Drupal\jsonapi\StackMiddleware\FormatSetter->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
 #35 /var/www/FOLDER/docroot/core/modules/ban/src/BanMiddleware.php(50): Asm89\Stack\Cors->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
 #36 /var/www/FOLDER/docroot/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\ban\BanMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
 #37 /var/www/FOLDER/docroot/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(52): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
 #38 /var/www/FOLDER/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
 #39 /var/www/FOLDER/docroot/core/lib/Drupal/Core/DrupalKernel.php(693): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true

Proposed resolution

The easiest hot-fix is to check that the resource type is present (not null) in ResourceIdentifier::toResourceIdentifier() before continuing along.

Will provide a PoC patch shortly.

Remaining tasks

TBD.

User interface changes

TBD.

API changes

TBD.

Data model changes

TBD.

Release notes snippet

TBD.