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', '1k9ongdumdp692viq8ndeots04', '54.224.255.158', '1498515578', '1498515578', '/shop_content.php?coID=7')

[XT SQL Error]