cupertino_http: `BaseResponse.request` is null

```dart
  final http.StreamedResponse res =
      await CupertinoClient.defaultSessionConfiguration().send(
    http.Request(
        'GET', Uri.parse('https://jsonplaceholder.typicode.com/users/1')),
  );
  print('res.request: ${res.request}');
```

Console:
```
flutter: res.request: null
```