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', '0f1pgqs5gtnk2av4p5gvf19eg1', '216.73.216.83', '1760429436', '1760429436', '/xtshop/index.php?cat=c52_.html')

[XT SQL Error]