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', '4k2jtme637la09a7rbqq1lc1n1', '216.73.216.208', '1765132664', '1765132664', '/xtshop/product_info.php?info=p403_.html')

[XT SQL Error]