Don't require non-empty Project-Id-Version
Don't require non-empty Project-Id-Version

GNU gettext tools require this header to be present and have non-default
value, but they don't require *non-empty* value. Poedit's catalog
properties window was being too strict for no real benefit.

Remove the check for non-empty project IDs. Makes setting up new POs
easier.

BenKeyFSI/poedit,PKRoma/poedit,PatidarWeb/poedit,PKRoma/poedit,huoxudong125/poedit,alexhenrie/poedit,huoxudong125/poedit,alexhenrie/poedit,vslavik/poedit,egoitzro/poedit,nawawi/poedit,nawawi/poedit,egoitzro/poedit,c72578/poedit,nawawi/poedit,dwaynebailey/poedit,dwaynebailey/poedit,PatidarWeb/poedit,nawawi/poedit,PatidarWeb/poedit,c72578/poedit,c72578/poedit,egoitzro/poedit,BenKeyFSI/poedit,PKRoma/poedit,dwaynebailey/poedit,PatidarWeb/poedit,vslavik/poedit,PKRoma/poedit,alexhenrie/poedit,BenKeyFSI/poedit,dwaynebailey/poedit,PatidarWeb/poedit,nawawi/poedit,BenKeyFSI/poedit,huoxudong125/poedit,babycaseny/poedit,c72578/poedit,vslavik/poedit,huoxudong125/poedit,egoitzro/poedit,vslavik/poedit,vslavik/poedit,huoxudong125/poedit,babycaseny/poedit,dwaynebailey/poedit,alexhenrie/poedit,PKRoma/poedit,babycaseny/poedit,egoitzro/poedit,babycaseny/poedit,c72578/poedit,alexhenrie/poedit,babycaseny/poedit,BenKeyFSI/poedit