Update to Validator->validateAccepted(), accounts for (int) 0 values ensuring that they do not validate

Currently an (int) 0 value will pass validation when the "Accepted" validation rule is applied.  It's my understanding that the intent of this rule is to strictly validate on 'yes', 'on' and (int) 1 values.

This fix adds an additional check to ensure that validation fails when the evaluated value is an exact match for (int) 0.