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### Preflight Checklist
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* [x] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
* [X] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [X] I have searched the issue tracker for an issue that matches the one I want to file, without success.

### Issue Details

* **Electron Version:**
  * 5.0.0
* **Operating System:**
  * macOS 10.14.4
* **Last Known Working Electron version:**:
  * 4.1.4

### Expected Behavior
Quitting while a debugger is attached to the process results in the application exiting without error.

### Actual Behavior
Qutting while a debugger is still attached results in the application crashing and macOS showing its crash report dialog.

### To Reproduce

1. Run electron with `--inspect=9229` or `--inspect-brk=9229`.
2. Attach with a debugger (such as Visual Studio Code).
3. Quit electron without detaching.

Below is a repo that reproduces the issue:
[Repo that reproduces the issue](https://github.com/kpes/electron5attachquitcrash)

```sh
$ git clone https://github.com/kpes/electron5attachquitcrash.git
$ npm install
```

atom/app/node_main.cc
do {
      more = uv_run(env->event_loop(), UV_RUN_ONCE);
      gin_env.platform()->DrainTasks(env->isolate());
      if (more == false) {
        node::EmitBeforeExit(env);
        
        
        more = uv_loop_alive(env->event_loop());
        if (uv_run(env->event_loop(), UV_RUN_NOWAIT) != 0)
          more = true;
      }
    } while (more == true);
    exit_code = node::EmitExit(env);
    node::RunAtExit(env);
    gin_env.platform()->DrainTasks(env->isolate());
    gin_env.platform()->CancelPendingDelayedTasks(env->isolate());
    gin_env.platform()->UnregisterIsolate(env->isolate());
    node::FreeEnvironment(env);
  }
  
  
  
  
  
  base::ThreadPool::GetInstance()->Shutdown();
  v8::V8::Dispose();
  return exit_code;
}
}