Create single processor on outside of various checks.

Author: dmsnell

src/wp-includes/block-supports/layout.php

@@ -589,14 +589,26 @@ function wp_render_layout_support_flag( $block_content, $block ) {
 		$outer_class_names[] = $container_content_class;
 	}
 
-	// Return early if only child layout exists.
+	// Prep the processor for modifying the block output.
+	$processor = new WP_HTML_Tag_Processor( $block_content );
+
+	// Having no tags implies there are no tags onto which to add class names.
+	if ( ! $processor->next_tag() ) {
+		return $block_content;
+	}
+
+	/*
+	 * Return early if only child layout exists.
+	 *
+	 * In other words, if there is nothing more complicated, add
+	 * the wrapper class names to the first HTML tag inside the
+	 * block's rendered HTML.
+	 */
 	if ( ! $support_layout && ! empty( $outer_class_names ) ) {
-		$content = new WP_HTML_Tag_Processor( $block_content );
-		$content->next_tag();
 		foreach ( $outer_class_names as $class_name ) {
-			$content->add_class( $class_name );
+			$processor->add_class( $class_name );
 		}
-		return $content->get_updated_html();
+		return $processor->get_updated_html();
 	}
 
 	$global_settings = wp_get_global_settings();