* 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_->FlashFrame(flash);
}
void Window::SetSkipTaskbar(bool skip) {
  window_->SetSkipTaskbar(skip);
}
void Window::SetSimpleFullScreen(bool simple_fullscreen) {
  window_->SetSimpleFullScreen(simple_fullscreen);
}
bool Window::IsSimpleFullScreen() {
  return window_->IsSimpleFullScreen();
}
void Window::SetKiosk(bool kiosk) {
  window_->SetKiosk(kiosk);
}
bool Window::IsKiosk() {
  return window_->IsKiosk();
}
void Window::SetBackgroundColor(const std::string& color_name) {
  window_->SetBackgroundColor(color_name);
}
void Window::SetHasShadow(bool has_shadow) {
  window_->SetHasShadow(has_shadow);
}
bool Window::HasShadow() {
  return window_->HasShadow();
}
void Window::SetOpacity(const double opacity) {
  window_->SetOpacity(opacity);
}
double Window::GetOpacity() {