diff --git a/includes/Data/ContentBlocksResolver.php b/includes/Data/ContentBlocksResolver.php
index 4f00900c..6262c4f7 100644
--- a/includes/Data/ContentBlocksResolver.php
+++ b/includes/Data/ContentBlocksResolver.php
@@ -251,7 +251,7 @@ private static function populate_post_content_inner_blocks( array $block ): arra
 	 * @return array<string,mixed> The populated block.
 	 */
 	private static function populate_navigation_blocks( array $block ): array {
-		if ( 'core/navigation' !== $block['blockName'] || ! isset( $block['attrs']['ref'] ) ) {
+		if ( ($block['blockName'] ?? '') !== 'core/navigation' || ! isset( $block['attrs']['ref'] ) ) {
 			return $block;
 		}