"Getter was called on null" error when i try to loop through a nested object in Flutter

i have an object that looks like this,

marketOptions: {option1: {optionValue: 'Yes', optionId: `${match.id}`+ '333'+ `1`}, option2:{optionValue: 'No', optionId: `${match.id}`+ '333'+ `2` }},

I want to loop through "option1", "option2", etc and collect the data in "optionValue", my first attempt below was to get the object from my Firestore database and assign it to a variable called "marketList" and then using a Listview.builder loop through the list but i keep getting the error "the getter "optionValue" was called on null", how can i achieve what i am looking for?

var marketList = thesnapshot.data()['marketOptions'];
var listCount = thesnapshot.data()['marketOptions'].length;



Container(height: listCount * MediaQuery.of(context).size.height * 11.8 / 100, child: ListView.builder(physics: const NeverScrollableScrollPhysics(),
                itemCount: listCount,
                itemBuilder: (context, index) {




                    return Column(
                            mainAxisAlignment: MainAxisAlignment.start,
                            crossAxisAlignment: CrossAxisAlignment.center,



                            children: < Widget > [Container(height: MediaQuery.of(context).size.height * 10 / 100, child: Row(
                                        mainAxisAlignment: MainAxisAlignment.start,
                                        crossAxisAlignment: CrossAxisAlignment.center,



                                        children: < Widget > [


                                            Container(width: MediaQuery.of(context).size.width * 40 / 100, child: Text(marketList[index].optionValue, style: TextStyle(
                                                color: Color(0xffffffff),
                                                fontFamily: 'Montserrat',
                                                fontSize: MediaQuery.of(context).size.height * 1.8 / 100,
                                                fontWeight: FontWeight.w600))),