Drupal 11.3 deprecation: ViewHandler passes NULL from failed Views renders to Renderer::render()

Project version

- DXPR Builder 2.8.0
- Also reproducible in 2.8.1-beta1
- Drupal 11.3.x
- PHP 8.3

### Problem/Motivation

Drupal\dxpr_builder\Service\Handler\ViewHandler::getView() assumes that ViewExecutable::render() always returns a render array:

$rendered_view = $view->render($displayId);
$output = $this->renderer->render($rendered_view);

However, ViewExecutable::render() is documented to return array|null. It returns NULL when the View build fails or access is denied, including cases such as:

- Contextual argument validation failures.
- A missing default contextual argument on routes without a current node.
- A View display whose build sets build_info['fail'].
- A View display whose build sets build_info['denied'].

DXPR Builder then passes that NULL value to Renderer::render().

Drupal 11.3 emits the following deprecation warning:

Calling Drupal\Core\Render\Renderer::render with NULL is deprecated in
drupal:11.3.0 and is removed from drupal:12.0.0. Either pass an array or
skip the call. See https://www.drupal.org/node/3534020.

This can produce a large number of log entries when a DXPR View element is included in a global block, such as a footer, and the View cannot resolve its contextual argument on login, 403, 404, or other non-node routes.

In Drupal 12, RendererInterface::render() will require an array, so this will become a compatibility error rather than only a deprecation warning.

### Steps to reproduce

1. Install Drupal 11.3.x and DXPR Builder 2.8.x.
2. Create a View with a contextual argument whose default value depends on the current node.
3. Add the View to a DXPR CMS View element.
4. Render the element on a route without a current node, or supply an invalid contextual argument that fails validation.
5. Check the Drupal logs.

### Actual result

The View returns NULL, and DXPR Builder calls:

$this->renderer->render(NULL);

Example stack trace:

Drupal\Core\Render\Renderer->render()
Drupal\dxpr_builder\Service\Handler\ViewHandler->getView()
Drupal\dxpr_builder\Service\DxprBuilderService->loadCmsElement()
Drupal\dxpr_builder\Service\DxprBuilderService->parseDocumentForCmsElements()
Drupal\dxpr_builder\Service\DxprBuilderService->parseForContent()
Drupal\dxpr_builder\Service\DxprBuilderService->updateHtml()
Drupal\dxpr_builder\Plugin\Field\FieldFormatter\DxprBuilderFormatter->viewElements()

### Expected result

DXPR Builder should detect the documented NULL return value and skip the renderer call.

The existing ViewHandlerInterface already permits a boolean return value, and DxprBuilderService::loadCmsElement() already handles falsey output by rendering an empty CMS element placeholder.

### Proposed resolution

Add a strict NULL guard before calling the renderer:

$rendered_view = $view->render($displayId);

if ($rendered_view === NULL) {
return FALSE;
}

$output = $this->renderer->render($rendered_view);

A strict comparison is preferable because an empty render array is valid and should continue through the normal rendering path.

### Remaining tasks

- Add the NULL guard to ViewHandler::getView().
- Add regression coverage for a View whose build fails.
- Confirm that attached libraries and drupalSettings continue to work for successful View renders.
- Confirm Drupal 12 compatibility.