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', 'sagjdpcbv0d9nvij7e4a1ioeb1', '216.73.217.62', '1783189440', '1783189440', '/index.php?XTCsid=38f09672db884903e3803adf9d076819&language=de')

[XT SQL Error]