Debugging 无颤振框架堆叠痕迹

我过去常常看到颤振框架抛出错误时的完整堆栈跟踪。但是，自最近发布以来，除了下面的消息外，没有显示堆栈轨迹

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:
════════════════════════════════════════════════════════

这里没有堆栈跟踪

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我在iOS上没有堆栈跟踪。不过我是在安卓系统上得到的。@DragonFax是的，没错。我现在才知道。