[Flutter] A non-null value must be returned since the return type ‘Widget’ doesn’t allow null

아래와 같이 future builder를 구성했는데 에러가 발생.

class _SomeState extends State<Some> {

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
      future: _getData(),
      builder: (context, snapshot) {
        Text('Testing');
      }
}

//error
lib/screens/some_list.dart:35:16: Error: A non-null value must be returned since the return type 'Widget' doesn't allow null.
 - 'Widget' is from 'package:flutter/src/widgets/framework.dart' ('../../../app/flutter/packages/flutter/lib/src/widgets/framework.dart').
      builder: (context, snapshot) {

builder안에서 return 해주면 해결. Widget을 return 하지 않아 발생한 에러.

class _SomeState extends State<Some> {

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
      future: _getData(),
      builder: (context, snapshot) {
        return Text('Testing');
      }
}