Repository: flutter
Issue: GoRouter errorBuilder - routes stack is cleared and there is no possibility to pop to previous screen
Labels: c: regression,package,has reproducible steps,P2,p: go_router,found in release: 3.3,found in release: 3.7,team-go_router,triaged-go_router

When you push some unknown route 
`context.push('/someRoute');`
errorBuilder widget is shown. But, there is no possibility to pop this error screen using leading icon of AppBar or system back button. 

This was possible in go_router version 3.1.1.

So, with latest version of go_router there is no possibility to push errorBuilder screen? It behaves like 'go' and not like 'push' because that errorBuilder screen cleans all previous routes stack even if previous there were push and pushNamed routes.



Previously with go_router version 3.1.1
I had:

```
import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';

void main() => runApp(const MyApp());

final GoRouter _router = GoRouter(
  routes: [
    GoRoute(
      path: '/',
      builder: (BuildContext context, GoRouterState state) {
        return const HomeScreen();
      },
      routes: [
        GoRoute(
          path: 'details',
          builder: (BuildContext context, GoRouterState state) {
            return const DetailsScreen();
          },
        ),
      ],
    ),
  ],
);

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      routeInformationParser: _router.routeInformationParser,
      routerDelegate: _router.routerDelegate,
    );
  }
}

class HomeScreen extends StatelessWidget {
  const HomeScreen({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Home Screen')),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            ElevatedButton(
              onPressed: () => context.push('/details'),
              child: const Text('Go to details screen'),
            ),
          ],
        ),
      ),
    );
  }
}

class DetailsScreen extends StatelessWidget {
  const DetailsScreen({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Details Screen')),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <ElevatedButton>[
            ElevatedButton(
              onPressed: () => context.push('/someRoute'),
              child: const Text('Go to unknown screen'),
            ),
          ],
        ),
      ),
    );
  }
}
```

And stack was working fine. When you press in Details screen button, error screen is shown and you can pop back to details screen. And then back to home screen. 

With newer version of the go_router you can't pop back. Same code as previous, only change is additional line in MaterialApp:
```
    return MaterialApp.router(
      routeInformationProvider: _router.routeInformationProvider,
      routeInformationParser: _router.routeInformationParser,
      routerDelegate: _router.routerDelegate,
    );
```