* 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_->SelectPreviousTab();
}
void Window::SelectNextTab() {
  window_->SelectNextTab();
}
void Window::MergeAllWindows() {
  window_->MergeAllWindows();
}
void Window::MoveTabToNewWindow() {
  window_->MoveTabToNewWindow();
}
void Window::ToggleTabBar() {
  window_->ToggleTabBar();
}
void Window::AddTabbedWindow(NativeWindow* window) {
  window_->AddTabbedWindow(window);
}
void Window::SetVibrancy(mate::Arguments* args) {
  std::string type;
  args->GetNext(&type);
  window_->SetVibrancy(type);
}
void Window::SetTouchBar(const std::vector<mate::PersistentDictionary>& items) {
  window_->SetTouchBar(items);
}
void Window::RefreshTouchBarItem(const std::string& item_id) {
  window_->RefreshTouchBarItem(item_id);
}
void Window::SetEscapeTouchBarItem(const mate::PersistentDictionary& item) {