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', '81r9v819lhm0rts4rhv2hppn91', '216.73.216.7', '1758233648', '1758233648', '/product_info.php?XTCsid=81fba26e1f006e30d12d9ee4d58a4030&info=p22_Plastic-tablecloth.html')

[XT SQL Error]