* 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_web_contents.cc
: embedder_(nullptr),
      zoom_controller_(nullptr),
      type_(BROWSER_WINDOW),
      request_id_(0),
      background_throttling_(true),
      enable_devtools_(true) {
  
  
  MarkHighMemoryUsage();
  
  options.Get("backgroundThrottling", &background_throttling_);
  
  
  
  
  
  bool b = false;
  if (options.Get("isGuest", &b) && b)
    type_ = WEB_VIEW;
  else if (options.Get("isBackgroundPage", &b) && b)
    type_ = BACKGROUND_PAGE;
  else if (options.Get("isBrowserView", &b) && b)
    type_ = BROWSER_VIEW;
#if defined(ENABLE_OSR)
  else if (options.Get("offscreen", &b) && b)
    type_ = OFF_SCREEN;
#endif
  
  options.Get("embedder", &embedder_);