Allowing null String in DateTime.parse()

Solution for Allowing null String in DateTime.parse()
is Given Below:

I am trying to format a String containing a date into a different Date format. I get the data from a Firestore document. When I pull the data into my UI of my flutter app I want to convert it to DateTime type so I can format it differently.
EDIT I added the suggested edit.

if (trxnProvider.sellerDisclosure24a != null && trxnProvider.sellerDisclosure24a != "") {
                final String? sellerDisclosure24a = trxnProvider.sellerDisclosure24a;
                _dt = DateTime.parse(sellerDisclosure24a);
                sellerDisclosure24aController.text = DateFormat('EE,  MM-dd-yyyy').format(_dt) ?? "";
              } else {
                sellerDisclosure24aController.text = "";
              }

However, I am getting the following error at this line

_dt = DateTime.parse(trxnProvider.sellerDisclosure24a);

The argument type ‘String?’ can’t be assigned to the parameter type ‘String’. (Documentation)
‘sellerDisclosure24a’ refers to a property so it couldn’t be promoted. See http://dart.dev/go/non-promo-property (trxn_provider.dart:55).

I have tried adding both “?” and “!” but I still get the error. How do I deal with this null safety issue? As you can see I am checking that data exists.

Just create a local copy of trxnProvider.sellerDisclosure24a and use it instead:

// A local copy!
final String? sellerDisclosure24a = trxnProvider.sellerDisclosure24a;

if (sellerDisclosure24a != null && sellerDisclosure24a != "") {
  _dt = DateTime.parse(sellerDisclosure24a);
  sellerDisclosure24aController.text = DateFormat('EE,  MM-dd-yyyy').format(_dt) ?? "";
} else {
  sellerDisclosure24aController.text = "";
}