Undefined index: gfp_v_id

PHP Notice: Undefined index: gfp_v_id in /path/to/wp-content/plugins/goaffpro/goaffpro.php on line 114

Updated from line 102:

/**
 * Add goaffpro referral cookie in woocommerce order metadata if referral cookie is available.
 * This helps in tagging the orders received with the unique ID of the affiliate who sent the customer
 */
add_action('woocommerce_checkout_update_order_meta',function( $order_id, $posted ) {
    if( isset( $_COOKIE['ref'] ) ) {
	    $referral_code = sanitize_text_field( $_COOKIE['ref'] );
	    if ( $referral_code ) {
		    update_post_meta( $order_id, 'ref', $referral_code );
	    }
    }
	if( isset( $_COOKIE['gfp_v_id'] ) ) {
		$visit_id = sanitize_text_field( $_COOKIE['gfp_v_id'] );
		if ( $visit_id ) {
			update_post_meta( $order_id, 'gfp_v_id', $visit_id );
		}
	}
} , 10, 2);