type 'null' is not subtype of type "widget"

someone help me plz. i can solve it .please solve this error .why show null is not subtype please solve this error

its textfiled code now plz solve this code.here we using textfiled code this called should called bulder

setDataTextField(data) {
    Column(
      children: [
        TextField(
          decoration: InputDecoration(fillColor: Colors.blue),
          controller: _nameController =
              TextEditingController(text: data['name']),
        ),
        TextField(
          decoration: InputDecoration(fillColor: Colors.blue),
          controller: _phoneController =
              TextEditingController(text: data['contract']),
        ),
        TextField(
          decoration: InputDecoration(fillColor: Colors.blue),
          controller: _dobController = TextEditingController(text: data['dob']),
        ),
        TextField(
          decoration: InputDecoration(fillColor: Colors.blue),
          controller: _genderController =
              TextEditingController(text: data['gender']),
        ),
        TextField(
          decoration: InputDecoration(fillColor: Colors.blue),
          controller: _ageController = TextEditingController(text: data['age']),
        ),
        SizedBox(
          height: 40.h,
        ),
        SizedBox(
          height: 56.h,
          width: 1.sw,
          child: ElevatedButton(
            onPressed: () {},
            child: Text(
              'UPDATE YOUR PROFILE',
              style: TextStyle(fontSize: 18.sp),
            ),
          ),
        ),
      ],
    );
  }

its stream builder code

StreamBuilder(
            stream: FirebaseFirestore.instance
                .collection('users-data-form')
                .doc(FirebaseAuth.instance.currentUser!.email)
                .snapshots(),
            builder: (BuildContext context, AsyncSnapshot snapshot) {
              var data = snapshot.data;
              return setDataTextField(data);
            },
          ),

>Solution :

setDataTextField should have return.
change it to this.

Widget SetDataTextField(dynamic data) {
    return Column(
      children: [...]);

and inside StreamBuilder you should wrap your code inside this condition:

if(snapshot.hasData){YourCode}

StreamBuilder(
            stream: FirebaseFirestore.instance
                .collection('users-data-form')
                .doc(FirebaseAuth.instance.currentUser!.email)
                .snapshots(),
            builder: (BuildContext context, AsyncSnapshot snapshot) {
              if(snapshot.hasData) {
                var data = snapshot.data;
                return setDataTextField(data);
              }
            },
          ),