Views: TypeError when $row->_entity is null in CustomElements style plugin

Problem/Motivation

The Custom Elements views style plugin crashes with a TypeError when a view result row has a null entity ($row->_entity === null). This can happen when an entity is deleted between the view query execution and entity rendering, e.g. during concurrent requests or cache race conditions.

TypeError: Drupal\custom_elements\CustomElementGenerator::generate(): Argument #1 ($entity) must be of type Drupal\Core\Entity\ContentEntityInterface, null given, called in lupus_decoupled_views/src/Plugin/views/style/CustomElements.php on line 86

Steps to reproduce

1. Create a view using the Custom Elements style with an entity row plugin
2. Have content that gets deleted or becomes unavailable between query and render time (e.g. via concurrent requests, cron, or automated test cleanup)
3. The view crashes instead of gracefully skipping the missing entity

This is hard to reproduce manually but occurs in automated testing environments where multiple operations happen in quick succession.

Proposed resolution

Add a null guard for $row->_entity in CustomElements::render() before passing it to CustomElementGenerator::generate(). Rows with null entities should be silently skipped, consistent with how Drupal core handles missing entities in views rendering.

Remaining tasks

User interface changes

API changes

Data model changes