Button Block: Add back compat for WP6.4 regarding HTML tag processor

packages/block-library/src/button/index.php

@@ -17,7 +17,20 @@
  * @return string The block content.
  */
 function render_block_core_button( $attributes, $content ) {
-	$p = new WP_HTML_Tag_Processor( $content );
+	/*
+	 * The current Gutenberg plugin supports WordPress 6.4, but the next_token()
+	 *  method does not exist in WordPress 6.4. Therefore, if Gutenberg is used
+	 * as a plugin, use the Gutenberg class that includes the next_token method.
+	 *
+	 * TODO: After the Gutenberg plugin drops support for WordPress 6.4, this
+	 * conditional statement will be removed and the core class `WP_HTML_Tag_Processor`
+	 * should be used.
+	 */
+	if ( defined( 'IS_GUTENBERG_PLUGIN' ) && IS_GUTENBERG_PLUGIN && class_exists( 'Gutenberg_HTML_Tag_Processor_6_5' ) ) {
+		$p = new Gutenberg_HTML_Tag_Processor_6_5( $content );
+	} else {
+		$p = new WP_HTML_Tag_Processor( $content );
+	}
 
 	/*
 	 * The button block can render an `<a>` or `<button>` and also has a