validate method
Validation that works in concert with the number accessor.
Implementation
@override
Map<String, dynamic>? validate(AbstractControl control) {
assert(control is Control);
// If the control doesn't have a value, but had a value from the input then
// it is considered an error. Producing error here as accessors can't easily
// add errors themselves, but validators can.
if (control.value == null && !isEmpty((control as Control).rawValue)) {
return {inputNotNumberErrorKey: inputIsNotNumberMsg()};
}
return null;
}