* 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
if (browser_view_.IsEmpty()) {
    return;
  }
  mate::Handle<BrowserView> browser_view;
  if (mate::ConvertFromV8(isolate(), GetBrowserView(), &browser_view)) {
    browser_view->web_contents()->SetOwnerWindow(nullptr);
  }
  browser_view_.Reset();
}
bool Window::IsModal() const {
  return window_->is_modal();
}
v8::Local<v8::Value> Window::GetNativeWindowHandle() {
  gfx::AcceleratedWidget handle = window_->GetAcceleratedWidget();
  return ToBuffer(
      isolate(), static_cast<void*>(&handle), sizeof(gfx::AcceleratedWidget));
}
void Window::SetVisibleOnAllWorkspaces(bool visible) {
  return window_->SetVisibleOnAllWorkspaces(visible);
}
bool Window::IsVisibleOnAllWorkspaces() {
  return window_->IsVisibleOnAllWorkspaces();
}
void Window::SetAutoHideCursor(bool auto_hide) {
  window_->SetAutoHideCursor(auto_hide);
}
void Window::SelectPreviousTab() {