* 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
if (icon->image().IsEmpty()) {
    args->ThrowError("Must specify non-empty 'icon' option");
    return;
  }
#endif
  
  if (!files.empty()) {
    base::MessageLoop::ScopedNestableTaskAllower allow(
        base::MessageLoop::current());
    DragFileItems(files, icon->image(), web_contents()->GetNativeView());
  } else {
    args->ThrowError("Must specify either 'file' or 'files' option");
  }
}
void WebContents::CapturePage(mate::Arguments* args) {
  gfx::Rect rect;
  base::Callback<void(const gfx::Image&)> callback;
  if (!(args->Length() == 1 && args->GetNext(&callback)) &&
      !(args->Length() == 2 && args->GetNext(&rect)
                            && args->GetNext(&callback))) {
    args->ThrowError();
    return;
  }
  const auto view = web_contents()->GetRenderWidgetHostView();
  if (!view) {
    callback.Run(gfx::Image());
    return;
  }
  
  const gfx::Size view_size = rect.IsEmpty() ? view->GetViewBounds().size() :