* 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
std::string display_name;
  if (!args->GetNext(&display_name))
    display_name = path;
  window_->PreviewFile(path, display_name);
}
void Window::CloseFilePreview() {
  window_->CloseFilePreview();
}
void Window::SetParentWindow(v8::Local<v8::Value> value,
                             mate::Arguments* args) {
  if (IsModal()) {
    args->ThrowError("Can not be called for modal window");
    return;
  }
  mate::Handle<Window> parent;
  if (value->IsNull()) {
    RemoveFromParentChildWindows();
    parent_window_.Reset();
    window_->SetParentWindow(nullptr);
  } else if (mate::ConvertFromV8(isolate(), value, &parent)) {
    parent_window_.Reset(isolate(), value);
    window_->SetParentWindow(parent->window_.get());
    parent->child_windows_.Set(isolate(), ID(), GetWrapper());
  } else {
    args->ThrowError("Must pass BrowserWindow instance or null");
  }
}
v8::Local<v8::Value> Window::GetParentWindow() const {