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', '4uc0frvektkt3hrnlg8f0vs082', '216.73.217.92', '1781008421', '1781008421', '/xtshop/account.php')

[XT SQL Error]