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', 'tgs3al97l3sd2fcn83bajqe1u0', '18.232.53.231', '1566527191', '1566527191', '/Impressum:_:4.html')

[XT SQL Error]