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', 'tcfmtvkimorv118e39034lm2k1', '216.73.216.244', '1752203902', '1752203902', '/index.php?cat=c5_Crockery.html&XTCsid=c5d9d9a5780af7d5707e3b2046ece3fe')

[XT SQL Error]