Electron Version: 7.1.1
Operating System: Windows 10 (1803)

If I set the 'margins' option when call webContents.print method,
The app will crash with no error message.

```js
let { remote } = require("electron");
let webContents = remote.getCurrentWebContents();
webContents.print(
  {
    margins: {
      marginType: "custom",
      top: 30,
      bottom: 0,
      left: 0,
      right: 0
    }
  },
  (success, errorType) => {
    if (!success) console.log(errorType);
  }
);
```

shell/browser/api/electron_api_web_contents.cc
} else if (type == blink::WebInputEvent::kMouseWheel) {
    blink::WebMouseWheelEvent mouse_wheel_event;
    if (gin::ConvertFromV8(isolate, input_event, &mouse_wheel_event)) {
      if (IsOffScreen()) {
#if BUILDFLAG(ENABLE_OSR)
        GetOffScreenRenderWidgetHostView()->SendMouseWheelEvent(
            mouse_wheel_event);
#endif
      } else {
        // Chromium expects phase info in wheel events (and applies a
        // DCHECK to verify it). See: https://crbug.com/756524.
        mouse_wheel_event.phase = blink::WebMouseWheelEvent::kPhaseBegan;
        mouse_wheel_event.dispatch_type = blink::WebInputEvent::kBlocking;
        rwh->ForwardWheelEvent(mouse_wheel_event);
        // Send a synthetic wheel event with phaseEnded to finish scrolling.
        mouse_wheel_event.has_synthetic_phase = true;
        mouse_wheel_event.delta_x = 0;
        mouse_wheel_event.delta_y = 0;
        mouse_wheel_event.phase = blink::WebMouseWheelEvent::kPhaseEnded;
        mouse_wheel_event.dispatch_type =
            blink::WebInputEvent::kEventNonBlocking;
        rwh->ForwardWheelEvent(mouse_wheel_event);
      }
      return;
    }
  }
  isolate->ThrowException(
      v8::Exception::Error(gin::StringToV8(isolate, "Invalid event object")));
}
void Ws::BeginFrameSubscription(gin_helper::Arguments* args) {