* 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
api_web_contents_->RemoveObserver(this);
  
  
  if (web_contents())
    Cleanup();
}
void BrowserWindow::OnInputEvent(const blink::WebInputEvent& event) {
  switch (event.GetType()) {
    case blink::WebInputEvent::kGestureScrollBegin:
    case blink::WebInputEvent::kGestureScrollUpdate:
    case blink::WebInputEvent::kGestureScrollEnd:
      Emit("scroll-touch-edge");
      break;
    default:
      break;
  }
}
void BrowserWindow::RenderViewHostChanged(content::RenderViewHost* old_host,
                                          content::RenderViewHost* new_host) {
  if (old_host)
    old_host->GetWidget()->RemoveInputEventObserver(this);
  if (new_host)
    new_host->GetWidget()->AddInputEventObserver(this);
}
void BrowserWindow::RenderViewCreated(