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', 'o2re8unbpt4ko15mcv6nlftmr2', '216.73.216.180', '1766257251', '1766257251', '/index.php?XTCsid=5771d82eee0b9754fa5c3ca98fd4f740')

[XT SQL Error]