[-] FO : Fix big on invalid gift message

Bug not found in forge :
While submitting an invalide gift message (including per example "<" character), processCarrier function attempts to include footer.php (which does not exist anymore ?) and then exits script, instead of letting the classic validate system running and showing an error.
Merge pull request #1360 from tomablan/patch-2

[-] FO : Fix bug on invalid gift message