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', 'q9f2bebn7uaa0vpen26tejok61', '216.73.216.244', '1752217851', '1752217851', '/product_info.php?info=p15_25-balloons.html&XTCsid=363052f8eb28c495db1ddeca225278d6')

[XT SQL Error]