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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/browser/atom_browser_main_parts.cc
#if defined(OS_LINUX)
  device::BluetoothAdapterFactory::Shutdown();
  bluez::DBusBluezManagerWrapperLinux::Shutdown();
#endif
  fake_browser_process_->PostDestroyThreads();
}
void AtomBrowserMainParts::ToolkitInitialized() {
  ui::MaterialDesignController::Initialize();
#if defined(USE_AURA) && defined(USE_X11)
  views::LinuxUI::instance()->Initialize();
#endif
#if defined(USE_AURA)
  wm_state_.reset(new wm::WMState);
#endif
#if defined(OS_WIN)
  gfx::win::SetAdjustFontCallback(&AdjustUIFont);
  gfx::win::SetGetMinimumFontSizeCallback(&GetMinimumFontSize);
  wchar_t module_name[MAX_PATH] = {0};
  if (GetModuleFileName(NULL, module_name, MAX_PATH))
    ui::CursorLoaderWin::SetCursorResourceModule(module_name);
#endif
#if defined(OS_MACOSX)
  views_delegate_.reset(new ViewsDelegateMac);
#else
  views_delegate_.reset(new ViewsDelegate);
#endif
}
void AtomBrowserMainParts::PreMainMessageLoopRun() {