* Electron version: 2.0.0-beta.4
* Operating system: macOS 10.13.3

### Expected behavior

A reload of the window works.

### Actual behavior

A reload of the window does not work.

### How to reproduce

* run VSCode exploration ([download](https://az764295.vo.msecnd.net/exploration/6bc3274250cc949c7fb1d654cbb6e59c8ddad697/VSCode-darwin-exploration.zip))
* run "Reload Window" command
* sometimes I see the window stay blank after doing so and checking the console I see:

```
Uncaught (in promise) Error: Cannot get property 'id' on missing remote object 3
Error: Cannot get property 'id' on missing remote object 3
    at throwRPCError (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/rpc-server.js:143:17)
    at EventEmitter.<anonymous> (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/rpc-server.js:384:7)
    at emitThree (events.js:136:13)
    at EventEmitter.emit (events.js:217:7)
    at WebContents.<anonymous> (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/api/web-contents.js:295:13)
    at emitTwo (events.js:126:13)
    at WebContents.emit (events.js:214:7)
    at throwRPCError (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/rpc-server.js:143:17)
    at EventEmitter.<anonymous> (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/rpc-server.js:384:7)
    at emitThree (events.js:136:13)
    at EventEmitter.emit (events.js:217:7)
    at WebContents.<anonymous> (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/browser/api/web-contents.js:295:13)
    at emitTwo (events.js:126:13)
    at WebContents.emit (events.js:214:7)
    at Object.exception (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/renderer/api/remote.js:209:30)
    at metaToValue (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/renderer/api/remote.js:213:28)
    at Object.descriptor.get [as id] (/Applications/Visual Studio Code - Exploration.app/Contents/Resources/electron.asar/renderer/api/remote.js:132:16)
    at file:///Applications/Visual%20Studio%20Code%20-%20Exploration.app/Contents/Resources/app/out/vs/workbench/electron-browser/bootstrap/index.js:11:97
    at new Promise (<anonymous>)
    at file:///Applications/Visual%20Studio%20Code%20-%20Exploration.app/Contents/Resources/app/out/vs/workbench/electron-browser/bootstrap/index.js:10:838
```
atom/browser/api/atom_api_web_contents.cc
.SetMethod("isLoadingMainFrame", &WebContents::IsLoadingMainFrame)
      .SetMethod("isWaitingForResponse", &WebContents::IsWaitingForResponse)
      .SetMethod("_stop", &WebContents::Stop)
      .SetMethod("_goBack", &WebContents::GoBack)
      .SetMethod("_goForward", &WebContents::GoForward)
      .SetMethod("_goToOffset", &WebContents::GoToOffset)
      .SetMethod("isCrashed", &WebContents::IsCrashed)
      .SetMethod("setUserAgent", &WebContents::SetUserAgent)
      .SetMethod("getUserAgent", &WebContents::GetUserAgent)
      .SetMethod("savePage", &WebContents::SavePage)
      .SetMethod("openDevTools", &WebContents::OpenDevTools)
      .SetMethod("closeDevTools", &WebContents::CloseDevTools)
      .SetMethod("isDevToolsOpened", &WebContents::IsDevToolsOpened)
      .SetMethod("isDevToolsFocused", &WebContents::IsDevToolsFocused)
      .SetMethod("enableDeviceEmulation", &WebContents::EnableDeviceEmulation)
      .SetMethod("disableDeviceEmulation", &WebContents::DisableDeviceEmulation)
      .SetMethod("toggleDevTools", &WebContents::ToggleDevTools)
      .SetMethod("inspectElement", &WebContents::InspectElement)
      .SetMethod("setIgnoreMenuShortcuts",
                 &WebContents::SetIgnoreMenuShortcuts)
      .SetMethod("setAudioMuted", &WebContents::SetAudioMuted)
      .SetMethod("isAudioMuted", &WebContents::IsAudioMuted)
      .SetMethod("undo", &WebContents::Undo)
      .SetMethod("redo", &WebContents::Redo)
      .SetMethod("cut", &WebContents::Cut)
      .SetMethod("copy", &WebContents::Copy)
      .SetMethod("paste", &WebContents::Paste)
      .SetMethod("pasteAndMatchStyle", &WebContents::PasteAndMatchStyle)
      .SetMethod("delete", &WebContents::Delete)
      .SetMethod("selectAll", &WebContents::SelectAll)