The value "None" for field "fieldname" in "modulename" is not one of the allowed options

Hi people, am trying to see the result of the code written about a module on my localhost ,so i go to tryton ,i filled out a formular but then when i typed to save the record ,there was an error “The value “None” for field “fieldname” in “modulename” is not one of the allowed options” despite the field has already been filled in and is not empty .
thanks in advance

It’s a bit difficult to help you without seeing some of your code (though it looks like a SelectionField error but you said you filled it so it shouldn’t be None).

Could you post an excerpt?