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', 'm7plem6votbmgpufgggd0256c4', '216.73.216.147', '1751834784', '1751834784', '/product_info.php?info=p9_Paper-Lantern.html&XTCsid=3e3fcef0642c69bbf707de3c0bc1cf9c')

[XT SQL Error]