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### Preflight Checklist
<!-- Please ensure you've completed the following steps by replacing [ ] with [x]-->

* [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/browser/atom_browser_main_parts.cc
#include "atom/browser/atom_browser_main_parts.h"
#include <utility>
#if defined(OS_LINUX)
#include <glib.h>  
#endif
#include "atom/app/atom_main_delegate.h"
#include "atom/browser/api/atom_api_app.h"
#include "atom/browser/api/trackable_object.h"
#include "atom/browser/atom_browser_client.h"
#include "atom/browser/atom_browser_context.h"
#include "atom/browser/atom_paths.h"
#include "atom/browser/atom_web_ui_controller_factory.h"
#include "atom/browser/browser.h"
#include "atom/browser/browser_process_impl.h"
#include "atom/browser/feature_list.h"
#include "atom/browser/javascript_environment.h"
#include "atom/browser/media/media_capture_devices_dispatcher.h"
#include "atom/browser/node_debugger.h"
#include "atom/browser/ui/devtools_manager_delegate.h"
#include "atom/common/api/electron_bindings.h"
#include "atom/common/application_info.h"
#include "atom/common/asar/asar_util.h"
#include "atom/common/node_bindings.h"
#include "atom/common/node_includes.h"
#include "base/base_switches.h"
#include "base/command_line.h"
#include "base/feature_list.h"
#include "base/message_loop/message_loop.h"
#include "base/path_service.h"