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', 'mit9p4m2lm1jj1hbhu5uml64m4', '3.90.207.89', '1561057766', '1561057766', '/')

[XT SQL Error]