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
bool Ws::SendIPCMessage(bool internal,
                                 bool send_to_all,
                                 const std::string& channel,
                                 v8::Local<v8::Value> args) {
  blink::CloneableMessage message;
  if (!gin::ConvertFromV8(isolate(), args, &message)) {
    isolate()->ThrowException(v8::Exception::Error(
        gin::StringToV8(isolate(), "Failed to serialize arguments")));
    return false;
  }
  return SendIPCMessageWithSender(internal, send_to_all, channel,
                                  std::move(message));
}
bool Ws::SendIPCMessageWithSender(bool internal,
                                           bool send_to_all,
                                           const std::string& channel,
                                           blink::CloneableMessage args,
                                           int32_t sender_id) {
  std::vector<content::RenderFrameHost*> target_hosts;
  if (!send_to_all) {
    auto* frame_host = ontents()->GetMainFrame();
    if (frame_host) {
      target_hosts.push_back(frame_host);
    }
  } else {
    target_hosts = ontents()->GetAllFrames();
  }
  for (auto* frame_host : target_hosts) {
    mojo::AssociatedRemote<mojom::ElectronRenderer> electron_renderer;
    frame_host->GetRemoteAssociatedInterfaces()->GetInterface(