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', '884db475b6a9a8dba1f403bc097408cd', '34.229.24.100', '1563488142', '1563488142', '/index.php/cat/c369_vouchers.html')

[XT SQL Error]