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', 'j9usl5nvbva5to5keeaild5o43', '216.73.216.147', '1751839440', '1751839440', '/index.php?cat=c4_Beer-Mugs.html&XTCsid=502c4d4f7753d1888d9a6ca985d5c9c9')

[XT SQL Error]