diff -r be944660c56a -r 3d72ae0968f4 wp/wp-includes/class-wp-widget.php
--- a/wp/wp-includes/class-wp-widget.php	Wed Sep 21 18:19:35 2022 +0200
+++ b/wp/wp-includes/class-wp-widget.php	Tue Sep 27 16:37:53 2022 +0200
@@ -365,7 +365,7 @@
 		$this->_set( $widget_args['number'] );
 		$instances = $this->get_settings();
 
-		if ( array_key_exists( $this->number, $instances ) ) {
+		if ( isset( $instances[ $this->number ] ) ) {
 			$instance = $instances[ $this->number ];
 
 			/**