WP_Nav_Menu_Widget::update( array $new_instance, array $old_instance )

Source

File: wp-includes/widgets/class-wp-nav-menu-widget.php

public function update( $new_instance, $old_instance ) {
		$instance = array();
		if ( ! empty( $new_instance['title'] ) ) {
			$instance['title'] = sanitize_text_field( $new_instance['title'] );
		}
		if ( ! empty( $new_instance['nav_menu'] ) ) {
			$instance['nav_menu'] = (int) $new_instance['nav_menu'];
		}
		return $instance;
	}