null check 질문

import 'package:flutter/material.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:contacts_service/contacts_service.dart';

void main()
{
  runApp(MaterialApp(
    home: MyApp(),
  ));
}

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {

  getPermission() async {
    var status = await Permission.contacts.status;
    if (status.isGranted) {
      print('허락됨');
      var contacts = await ContactsService.getContacts();
      setState(() {
        name=contacts;
      });

    } else if (status.isDenied) {
      print('거절됨');
      Permission.contacts.request();
    }
  }

  var name=[];

  addName(a){
    setState(() {
      name.add(a);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        child: Text('button'),
        onPressed: (){
          showDialog(context: context, builder: (context){
            return DialogUI(addName:addName);
          });
        },
      ),
      appBar: AppBar(
        title: Text('연락처',style: TextStyle(fontSize: 30)),actions: [
          IconButton(onPressed: (){
            getPermission();
          }, icon: Icon(Icons.contacts))
      ],
      ),
      body: ListView.builder(
          itemCount: name.length,
          itemBuilder: (c,i){
            return ListTile(
              leading: Text((i+1).toString()),
              title: Text(name[i].displayName ?? '이름없음'),
              trailing: ElevatedButton(
                child: Text('삭제'),
                onPressed: (){
                  setState(() {
                    name.removeAt(i);
                  });
                },
              )
            );
          }),
    );
  }
}

class DialogUI extends StatelessWidget {
   DialogUI({Key? key,this.addName}) : super(key: key);
   final addName;
   var inputData=TextEditingController();
  @override

  Widget build(BuildContext context) {
    return Dialog(
      child: SizedBox(
        width: 300,
        height: 300,
        child: Column(
          children: [
            TextField(controller: inputData),
            TextButton(onPressed: (){
              if(inputData.text=='') {
                Navigator.pop(context);
              }
              else {
                Navigator.pop(context);
                var newPerson = Contact();
                newPerson.givenName = inputData.text;
                ContactsService.addContact(newPerson);
                addName(newPerson);
              }
            }, child: Text('완료')),
            TextButton(onPressed: (){
              Navigator.pop(context);
            }, child: Text('취소'))
          ],
        ),
      ),
    );
  }
}

이코드에서 appbar에있는 연락처불러오기 버튼 눌렀을때 전화번호 저장이 되어있어도 1번은 무조건 null이 나오는데 왜이런건가요 ??