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
Emit("zoom-changed", zoom_in ? "in" : "out");
}
void Ws::EnterFullscreenModeForTab(
    content::Ws* source,
    const GURL& origin,
    const blink::mojom::FullscreenOptions& options) {
  auto* permission_helper =
      WsPermissionHelper::FromWs(source);
  auto callback =
      base::BindRepeating(&Ws::OnEnterFullscreenModeForTab,
                          base::Unretained(this), source, origin, options);
  permission_helper->RequestFullscreenPermission(callback);
}
void Ws::OnEnterFullscreenModeForTab(
    content::Ws* source,
    const GURL& origin,
    const blink::mojom::FullscreenOptions& options,
    bool allowed) {
  if (!allowed)
    return;
  CommonWsDelegate::EnterFullscreenModeForTab(source, origin, options);
  Emit("enter-html-full-screen");
}
void Ws::ExitFullscreenModeForTab(content::Ws* source) {