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', 'gtlju0jglf4usj8i0o3v8i6vm2', '18.234.88.196', '1558467381', '1558467381', '/lkw_plane_tasche_lkw_plane/product_info.php/info/p115_Tasche-30-25-10-wei--dunkelgr-n-mit-sitzendem-Hund-in-dunkelgr.html')

[XT SQL Error]