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', 'ob59bf709rgk1ackokt33ljsm1', '216.73.216.7', '1758271868', '1758271868', '/shop_content.php?XTCsid=db2af6059aca9c6e759bf8459213e9e9&coID=2')

[XT SQL Error]