### Issue Details

* **Electron Version:**
  * 13.0.0-nightly.20201203
* **Operating System:**
  * macOS
* **Last Known Working Electron version:**
  * N/A

### Expected Behavior
`WebFrameMain.frames` should never contain undefined

### Actual Behavior
```
Uncaught Exception:
TypeError: Cannot read property 'processId' of undefined
    at id (/private/var/folders/_7/jm5cr84j7jd4v7btf2d3bqwm0000gn/T/tmp-59557-p4DTr3KWOsNk/main.js:4:38)
    at pft (/private/var/folders/_7/jm5cr84j7jd4v7btf2d3bqwm0000gn/T/tmp-59557-p4DTr3KWOsNk/main.js:6:36)
    at Timeout._onTimeout (/private/var/folders/_7/jm5cr84j7jd4v7btf2d3bqwm0000gn/T/tmp-59557-p4DTr3KWOsNk/main.js:27:5)
    at listOnTimeout (internal/timers.js:554:17)
    at processTimers (internal/timers.js:497:7)
```

### To Reproduce
Run https://gist.github.com/f46823470955034b4a456b6275862bfb for a short while and you'll observe the above error.

cc @samuelmaddock 

shell/browser/api/electron_api_web_frame_main.cc
base::BindOnce([](gin_helper::Promise<base::Value> promise,
                        base::Value value) { promise.Resolve(value); },
                     std::move(promise)),
      world_id);
  return handle;
}
bool WebFrameMain::Reload() {
  if (!CheckRenderFrame())
    return false;
  return render_frame_->Reload();
}
void WebFrameMain::Send(v8::Isolate* isolate,
                        bool internal,
                        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;
  }
  if (!CheckRenderFrame())
    return;
  mojo::AssociatedRemote<mojom::ElectronRenderer> electron_renderer;
  render_frame_->GetRemoteAssociatedInterfaces()->GetInterface(
      &electron_renderer);
  electron_renderer->Message(internal, channel, std::move(message),
                             0 );
}
void WebFrameMain::PostMessage(v8::Isolate* isolate,