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', '4mi8r6vu69se2j64rmr66olae0', '54.224.255.158', '1498515494', '1498515494', '/product_info.php?info=p139_Held.html')

[XT SQL Error]