Selecting the wrong widget in a Facet for a Rest export causes an exception and a white page

Hi all,

Testing another issue I had to set up a Facet for a Search API view, a REST export display. Being my first time I saved with the default values, and I got a white page with an error. Later I realized that I had to select the "Array with raw results" option for the Widget, but it wasn't evident to me that this was needed.

Would it be possible to add maybe some description to the widget selection field? I don't know if it's possible to catch the Exception and fail more gracefully.

The Exception shown and the trace is the following one:

Symfony\Component\Serializer\Exception\UnexpectedValueException: Could not normalize object of type Drupal\Core\Url, no supporting normalizer found. in Symfony\Component\Serializer\Serializer->normalize() (line 149 of /var/www/drupal8/vendor/symfony/serializer/Serializer.php).
Symfony\Component\Serializer\Serializer->normalize(Array, 'json', Array) (Line: 138)
Symfony\Component\Serializer\Serializer->normalize(Array, 'json', Array) (Line: 138)
Symfony\Component\Serializer\Serializer->normalize(Array, 'json', Array) (Line: 138)
Symfony\Component\Serializer\Serializer->normalize(Array, 'json', Array) (Line: 138)
Symfony\Component\Serializer\Serializer->normalize(Array, 'json', Array) (Line: 138)
Symfony\Component\Serializer\Serializer->normalize(Array, 'json', Array) (Line: 101)
Symfony\Component\Serializer\Serializer->serialize(Array, 'json', Array) (Line: 94)
Drupal\rest_facets\Plugin\views\style\FacetsSerializer->render() (Line: 390)
Drupal\rest\Plugin\views\display\RestExport->Drupal\rest\Plugin\views\display\{closure}() (Line: 574)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 391)
Drupal\rest\Plugin\views\display\RestExport->render() (Line: 1520)
Drupal\views\ViewExecutable->render() (Line: 381)
Drupal\rest\Plugin\views\display\RestExport->execute() (Line: 1617)
Drupal\views\ViewExecutable->executeDisplay('rest_export_1', Array) (Line: 78)
Drupal\views\Element\View::preRenderViewElement(Array)
call_user_func(Array, Array) (Line: 376)
Drupal\Core\Render\Renderer->doRender(Array, 1) (Line: 195)
Drupal\Core\Render\Renderer->render(Array, 1) (Line: 139)
Drupal\Core\Render\Renderer->Drupal\Core\Render\{closure}() (Line: 574)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 140)
Drupal\Core\Render\Renderer->renderRoot(Array) (Line: 364)
Drupal\rest\Plugin\views\display\RestExport::buildResponse('shapes', 'rest_export_1', Array) (Line: 52)
Drupal\views\Routing\ViewPageController->handle('shapes', 'rest_export_1', Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 574)
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}()
call_user_func_array(Object, Array) (Line: 144)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 64)
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: 50)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 652)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)