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', '6cqtihfcrn4gr6fa1n4g7d1ui1', '216.73.216.244', '1752213828', '1752213828', '/index.php?XTCsid=cc2df0871f5f3d52a88b086fc6d31ad8')

[XT SQL Error]