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', 'boc88utfob9ujhblej59b2nfv3', '54.81.195.240', '1511298898', '1511298898', '/shop/create_account.php')

[XT SQL Error]