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', 'ctsgv11drffqt5sc0mqbud9ht4', '216.73.217.69', '1790620838', '1790620838', '/xtshop/product_info.php?info=p1021_.html')

[XT SQL Error]