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', 'e1rn9tpgg70bld873hhrc896t1', '216.73.216.113', '1752187161', '1752187161', '/xtshop/product_info.php?info=p833_.html')

[XT SQL Error]