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', 'hbi7rn7npcb6h1u6efuq7aavd6', '216.73.216.244', '1752204018', '1752204018', '/index.php?cat=c5_Crockery.html&XTCsid=c407ede434192d8d024c7c2f06b2be8c')

[XT SQL Error]