没有颤振的框架堆栈跟踪

Question

当Flutter框架抛出错误时，我曾经看到完整的堆栈跟踪。但是，自最近发布以来，除了以下消息之外，没有显示堆栈跟踪。

完整代码

import 'package:flutter/material.dart';

class BtnApp extends StatelessWidget {
  final String title;

  BtnApp([this.title]);

  @override
  Widget build(BuildContext context) {
    if (title.substring(0, 1) == '/') {
      print('start with /');
    } else {
      print('other');
    }
    return new Container();
  }
}

main() {
  runApp(new BtnApp());
}

输出

Launching lib/tinker/btnapp.dart on iPhone 7 in debug mode...
Running pod install...
Running Xcode build...
Syncing files to device iPhone 7...
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞════════
The method 'substring' was called on null.
Receiver: null

When the exception was thrown, this was the stack:
════════════════════════════════════════════════════════

此处没有堆栈跟踪