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', 'lv3pl48clrd0eotse894hc6ku3', '216.73.216.144', '1781071653', '1781071653', '/xtshop/product_info.php?info=p727_.html')

[XT SQL Error]