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', '8a5e34s1u4k9t6bi2lvhldn7e0', '216.73.216.9', '1758140941', '1758140941', '/index.php?XTCsid=8b7cba01600c404a966486e68846ce8d')

[XT SQL Error]