Ticket #24577: default-widgets.php.patch

/wp-includes/

@@ -596 +596 @@
                 $instance = $old_instance;
                 $instance['title'] = strip_tags($new_instance['title']);
                 $instance['number'] = (int) $new_instance['number'];
-                $instance['show_date'] = (bool) $new_instance['show_date'];
+                $instance['show_date'] = isset( $new_instance['show_date'] ) ? (bool) $new_instance['show_date'] : false;
                 $this->flush_widget_cache();
 
                 $alloptions = wp_cache_get( 'alloptions', 'options' );