* Electron version: 1.6.15
* Operating system: Linux

### Expected behavior

Open a `BrowserWindow` with passed options

### Actual behavior

  - Usually a Segmentation fault.
  - Sometimes `[12843:0100/000000.043847:FATAL:zygote_linux.cc(479)] Failed to synchronise with parent zygote process`
  - Sometimes `[12819:0100/000000.719122:FATAL:zygote_linux.cc(509)] Check failed: len > 0 (0 vs. 0)`

### How to reproduce

I'm still working on making a smaller reproduction case. The issue goes away with small tweaks.

1. Starting from https://github.com/daurnimator/fengari-electron-example
2. Modify main.lua to contain:
```lua
local js = require "js"
local electron = require "electron"

electron.app:on("ready", function()
	local win = js.new(electron.BrowserWindow, js.createproxy({
		backgroundColor = '#2e2c29';
	}, "object"))
	win:loadURL("https://fengari.io")
end)
```

atom/browser/api/atom_api_window.cc
window_.reset(NativeWindow::Create(
      web_contents->managed_web_contents(),
      options,
      parent.IsEmpty() ? nullptr : parent->window_.get()));
  web_contents->SetOwnerWindow(window_.get());
  window_->set_is_offscreen_dummy(api_web_contents_->IsOffScreen());
#if defined(TOOLKIT_VIEWS)
  
  mate::Handle<NativeImage> icon;
  if (options.Get(options::kIcon, &icon))
    SetIcon(icon);
#endif
  window_->InitFromOptions(options);
  window_->AddObserver(this);
  InitWith(isolate, wrapper);
  AttachAsUserData(window_.get());
  
  
  if (!parent.IsEmpty())
    parent->child_windows_.Set(isolate, ID(), wrapper);
}
Window::~Window() {
  if (!window_->IsClosed())
    window_->CloseContents(nullptr);
  
  
  base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, window_.release());
}
void Window::WillCloseWindow(bool* prevent_default) {