Travel Booking – Warning: Cannot modify header information

Hi,

I have this error :

Warning: Cannot modify header information – headers already sent by (output started at /homepages/28/d750059116/htdocs/clickandbuilds/Destineo/wp-content/plugins/travel-booking/inc/product-type-tour.php:40) in /homepages/28/d750059116/htdocs/clickandbuilds/Destineo/wp-admin/includes/misc.php on line 1310

Warning: Cannot modify header information – headers already sent by (output started at /homepages/28/d750059116/htdocs/clickandbuilds/Destineo/wp-content/plugins/travel-booking/inc/product-type-tour.php:40) in /homepages/28/d750059116/htdocs/clickandbuilds/Destineo/wp-admin/admin-header.php on line 9

Danke