* Electron Version: v3.0.0-beta.2
* Operating System (Platform and Version): macOS 10.13.5
* Last known working Electron version: v3.0.0-beta.1

**Expected Behavior**
Launching DevTools

**Actual behavior**
Electron crash with current dump:
```
Crashing on exception: *** -[__NSArrayM objectAtIndex:]: index 1 beyond bounds [0 .. 0]

Application Specific Backtrace 1:
0   CoreFoundation                      0x00007fff489d332b __exceptionPreprocess + 171
1   libobjc.A.dylib                     0x00007fff6fb41c76 objc_exception_throw + 48
2   CoreFoundation                      0x00007fff48a14634 _CFThrowFormattedException + 202
3   CoreFoundation                      0x00007fff488f2290 __CFStringDecodeByteStream3 + 0
4   Electron Framework                  0x000000010e7554c2 _ZN9brightray8IOThread7CleanUpEv + 2210
...
```

**Additional info** 
`BrowserWindow` should contain `titleBarStyle` with `hiddenInset` value.

Full dump attached to [link](https://github.com/electron/electron/files/2185677/dump.txt)

atom/browser/api/atom_api_browser_window.cc
existing_preferences->Merge(web_preferences_dict);
    }
  } else {
    
    web_contents = WebContents::Create(isolate, web_preferences);
  }
  web_contents_.Reset(isolate, web_contents.ToV8());
  api_web_contents_ = web_contents.get();
  api_web_contents_->AddObserver(this);
  Observe(api_web_contents_->web_contents());
  
  mate::Dictionary(isolate, web_contents->GetWrapper())
      .Set("browserWindowOptions", options);
  
  
  ui::GpuSwitchingManager::SetTransparent(window()->transparent());
  
  web_contents->SetOwnerWindow(window());
  auto* host = web_contents->web_contents()->GetRenderViewHost();
  if (host)
    host->GetWidget()->AddInputEventObserver(this);
  InitWith(isolate, wrapper);
#if defined(OS_MACOSX)
  if (!window()->has_frame())
    OverrideNSWindowContentView();
#endif
  
  window()->InitFromOptions(options);
}
BrowserWindow::~BrowserWindow() {