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', 'i62kutm6u3v0tvl3isa72supu3', '216.73.216.9', '1758054919', '1758054919', '/index.php?XTCsid=97ffde802d8fc2c9d25f5f8b5828f81a')

[XT SQL Error]