[Zope] problem attach file / Zfile

[Frederique Blondelle]

Hello,

I have created a zclass with zfile as basic class.
With this class, users could, via a web form, send an attached file if 
they want.
With zope 2.5 (my previous version) if users don't attach a file, there 
is no problem
with zope 2.10, if there is no file attached, I have an error message : 
'file not specified". It seems that  attach  file is mandatory.

Who could help me

THanks