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', 'sb49q71t76o2ircl1u57rks0c0', '13.58.3.158', '1746786761', '1746786761', '/xtshop/index.php?cat=c11_.html')

[XT SQL Error]