[gdpr] Can not clear account erasure notification

I am on version 1.0-beta3 and flarum 1.8.10

I got an account erasure request which I complied with, but now there is an notification in Flarum for it that causes an error when I try to dismiss it.

The logs show:

```
[2025-07-22 20:27:28] flarum.ERROR: TypeError: Flarum\Gdpr\Api\Serializer\RequestErasureSerializer::user(): Return value must be of type Tobscure\JsonApi\Relationship, null returned in /flarum/forum/vendor/flarum/gdpr/src/Api/Serializer/RequestErasureSerializer.php:41
Stack trace:
#0 /flarum/forum/vendor/sycho/json-api/src/AbstractSerializer.php(79): Flarum\Gdpr\Api\Serializer\RequestErasureSerializer->user()
flarum/gdpr#1 /flarum/forum/vendor/flarum/core/src/Api/Serializer/AbstractSerializer.php(132): Tobscure\JsonApi\AbstractSerializer->getRelationship()
flarum/gdpr#2 flarum/forum/vendor/sycho/json-api/src/Resource.php(291): Flarum\Api\Serializer\AbstractSerializer-getRelationship()
flarum/gdpr#3 /flarum/forum/vendor/sycho/json-api/src/Resource.php(246): Tobscure\JsonApi\Resource->buildRelationships()
flarum/gdpr#4 /flarum/forum/vendor/sycho/json-api/src/Resource.php(268): Tobscure\JsonApi\Resource->getRelationships()
flarum/gdpr#5 /flarum/forum/vendor/sycho/json-api/src/Resource.php(87): Tobscure\JsonApi\Resource-getRelationshipsAsArray()
flarum/gdpr#6 /flarum/forum/vendor/sycho/json-api/src/Collection.php(113): Tobscure\JsonApi\Resource->toArray()
flarum/gdpr#7 [internal function]: Tobscure\JsonApi\Collection->Tobscure\JsonApi\{closure}()
flarum/gdpr#8 /flarum/forum/vendor/sycho/json-api/src/Collection.php(112): array_map()
flarum/gdpr#9 /flarum/forum/vendor/sycho/json-api/src/Document.php(188): Tobscure\JsonApi\Collection->toArray()
flarum/gdpr#10 /flarum/forum/vendor/sycho/json-api/src/Document.php(232): Tobscure\JsonApi\Document->toArray()
flarum/gdpr#11 /flarum/forum/vendor/flarum/core/src/Api/JsonApiResponse.php(27): Tobscure\JsonApi\Document-jsonSerialize()
flarum/gdpr#12 /flarum/forum/vendor/flarum/core/src/Api/Controller/AbstractSerializeController.php(139): Flarum\Api\JsonApiResponse->__construct()
flarum/gdpr#13 /flarum/forum/vendor/flarum/core/src/Http/RouteHandlerFactory.php(41): Flarum\Api\Controller\AbstractSerializeController->handle()
flarum/gdpr#14 /flarum/forum/vendor/flarum/core/src/Http/Middleware/ExecuteRoute.php(27): Flarum\Http\RouteHandlerFactory-Flarum\Http\{closure}()
flarum/gdpr#15 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\ExecuteRoute-process()
flarum/gdpr#16 /flarum/forum/vendor/fof/reactions/src/Middleware/BindRequestToContainer.php(35): Laminas\Stratigility\Next->handle()
flarum/gdpr#17 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): FoF\Reactions\Middleware\BindRequestToContainer->process()
flarum/gdpr#18 /flarum/forum/vendor/fof/oauth/src/Middleware/BindRequest.php(33): Laminas\Stratigility\Next->handle()
flarum/gdpr#19 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): FoF\OAuth\Middleware\BindRequest-process()
flarum/gdpr#20 /flarum/forum/vendor/flarum/core/src/Api/Middleware/ThrottleApi.php(33): Laminas\Stratigility\Next->handle()
flarum/gdpr#21 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Api\Middleware\ThrottleApi-process()
flarum/gdpr#22 /flarum/forum/vendor/flarum/core/src/Http/Middleware/CheckCsrfToken.php(36): Laminas\Stratigility\Next-handle()
flarum/gdpr#23 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\CheckCsrfToken->process()
flarum/gdpr#24 /flarum/forum/vendor/flarum/core/src/Http/Middleware/ResolveRoute.php(69): Laminas\Stratigility\Next-handle()
flarum/gdpr#25 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\ResolveRoute-process()
flarum/gdpr#26 /flarum/forum/vendor/flarum/core/src/Http/Middleware/SetLocale.php(51): Laminas\Stratigility\Next->handle()
flarum/gdpr#27 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\SetLocale->process()
flarum/gdpr#28 /flarum/forum/vendor/flarum/core/src/Http/Middleware/AuthenticateWithHeader.php(58): Laminas\Stratigility\Next->handle()
flarum/gdpr#29 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\AuthenticateWithHeader->process()
flarum/gdpr#30 /flarum/forum/vendor/flarum/core/src/Http/Middleware/AuthenticateWithSession.php(31): Laminas\Stratigility\Next->handle()
flarum/gdpr#31 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\AuthenticateWithSession->process()
flarum/gdpr#32 /flarum/forum/vendor/flarum/core/src/Http/Middleware/RememberFromCookie.php(63): Laminas\Stratigility\Next->handle()
flarum/gdpr#33 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\RememberFromCookie->process()
flarum/gdpr#34 /flarum/forum/vendor/flarum/core/src/Http/Middleware/StartSession.php(61): Laminas\Stratigility\Next->handle()
flarum/gdpr#35 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\StartSession->process()
flarum/gdpr#36 /flarum/forum/vendor/flarum/core/src/Api/Middleware/FakeHttpMethods.php(29): Laminas\Stratigility\Next->handle()
flarum/gdpr#37 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Api\Middleware\FakeHttpMethods->process()
flarum/gdpr#38 /flarum/forum/vendor/flarum/core/src/Http/Middleware/ParseJsonBody.php(28): Laminas\Stratigility\Next->handle()
flarum/gdpr#39 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\ParseJsonBody-process()
flarum/gdpr#40 /flarum/forum/vendor/flarum/core/src/Http/Middleware/HandleErrors.php(57): Laminas\Stratigility\Next-handle()
flarum/gdpr#41 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\HandleErrors-process()
flarum/gdpr#42 /flarum/forum/vendor/flarum/core/src/Http/Middleware/InjectActorReference.php(25): Laminas\Stratigility\Next->handle()
flarum/gdpr#43 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\InjectActorReference->process()
flarum/gdpr#44 /flarum/forum/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(81): Laminas\Stratigility\Next->handle()
flarum/gdpr#45 /flarum/forum/vendor/middlewares/request-handler/src/RequestHandler.php(84): Laminas\Stratigility\MiddlewarePipe->process()
flarum/gdpr#46 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Middlewares\RequestHandler->process()
flarum/gdpr#47 /flarum/forum/vendor/middlewares/base-path-router/src/BasePathRouter.php(97): Laminas\Stratigility\Next-handle()
flarum/gdpr#48 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Middlewares\BasePathRouter->process()
flarum/gdpr#49 /flarum/forum/vendor/laminas/laminas-stratigility/src/Middleware/OriginalMessages.php(36): Laminas\Stratigility\Next->handle()
flarum/gdpr#50 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Laminas\Stratigility\Middleware\OriginalMessages->process()
flarum/gdpr#51 /flarum/forum/vendor/middlewares/base-path/src/BasePath.php(73): Laminas\Stratigility\Next->handle()
flarum/gdpr#52 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Middlewares\BasePath->process()
flarum/gdpr#53 /flarum/forum/vendor/flarum/core/src/Http/Middleware/ProcessIp.php(24): Laminas\Stratigility\Next->handle()
flarum/gdpr#54 /flarum/forum/vendor/laminas/laminas-stratigility/src/Next.php(49): Flarum\Http\Middleware\ProcessIp->process()
flarum/gdpr#55 /flarum/forum/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(81): Laminas\Stratigility\Next-handle()
flarum/gdpr#56 /flarum/forum/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(70): Laminas\Stratigility\MiddlewarePipe->process()
flarum/gdpr#57 /flarum/forum/vendor/laminas/laminas-httphandlerrunner/src/RequestHandlerRunner.php(73): Laminas\Stratigility\MiddlewarePipe-handle()
flarum/gdpr#58 /flarum/forum/vendor/flarum/core/src/Http/Server.php(45): Laminas\HttpHandlerRunner\RequestHandlerRunner->run()
flarum/gdpr#59 /flarum/forum/public/index.php(28): Flarum\Http\Server->listen()
flarum/gdpr#60 {main}
```