1366 - Incorrect integer value: '' for column 'customer_id' at row 1

insert into whos_online (customer_id, full_name, session_id, ip_address, time_entry, time_last_click, last_page_url) values ('', 'Guest', 'ibkdbv8kedu3u260cgtq9lckd5', '216.73.216.197', '1751521220', '1751521220', '/product_info.php?language=de&info=p17_20-Tissue-Napkins.html&XTCsid=363052f8eb28c495db1ddeca225278d6')

[XT SQL Error]