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', '75465bbff51a45f2715adc6cd8348d55', '216.73.216.42', '1763383776', '1763383776', '/shop/product_info.php?info=p38_.html')

[XT SQL Error]