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', 'nnpid6mpgui4rdfsq267cnldq1', '216.73.216.147', '1751758032', '1751758032', '/product_info.php?info=p2_Bavarian-Pennant-Chain.html&XTCsid=adc8c520bddaa9e02a40df1e2a90f128')

[XT SQL Error]