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', 'r81j1fpg8tqdjun19jni02jim3', '18.190.176.26', '1746767858', '1746767858', '/xtshop/index.php?cat=c21_.html')

[XT SQL Error]