Wolfgang Ziegler
--- a/src/CustomElementsBlockRenderHelperTrait.php
+++ b/src/CustomElementsBlockRenderHelperTrait.php
+   * Converts a single block render array to a custom element.
+   *
+   * @param array $block_build
+   *   The block render array.
+   * @param \Drupal\Core\Cache\RefinableCacheableDependencyInterface|null $cache_metadata
+   *   Optional object to attach cache metadata to when the block is
+   *   empty (cache-only). Pass this to ensure cache metadata from empty
+   *   blocks is not lost.
+   *
+   * @return \Drupal\custom_elements\CustomElement|null
+   *   The custom element, or NULL if the block is empty and cache metadata
+   *   was attached to the provided cache metadata object.
+   */
+  public function convertBlockRenderArray(array $block_build, ?RefinableCacheableDependencyInterface $cache_metadata = NULL): ?CustomElement {
+    // Handle empty cache-only entries.
+    if (isset($block_build['#cache']) && count($block_build) == 1) {