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', '8k4cdtlhhs253ov3it40pfm2p6', '216.73.216.31', '1774985823', '1774985823', '/shop_content.php?XTCsid=e990f3916c880610adc34c2fa7d30f83&coID=8')

[XT SQL Error]