* 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
web_contents()->StopFinding(action);
}
void WebContents::ShowDefinitionForSelection() {
#if defined(OS_MACOSX)
  const auto view = web_contents()->GetRenderWidgetHostView();
  if (view)
    view->ShowDefinitionForSelection();
#endif
}
void WebContents::CopyImageAt(int x, int y) {
  const auto host = web_contents()->GetMainFrame();
  if (host)
    host->CopyImageAt(x, y);
}
void WebContents::Focus() {
  web_contents()->Focus();
}
#if !defined(OS_MACOSX)
bool WebContents::IsFocused() const {
  auto view = web_contents()->GetRenderWidgetHostView();
  if (!view) return false;
  if (GetType() != BACKGROUND_PAGE) {
    auto window = web_contents()->GetNativeView()->GetToplevelWindow();
    if (window && !window->IsVisible())
      return false;
  }
  return view->HasFocus();
}
#endif
void WebContents::TabTraverse(bool reverse) {