### Preflight Checklist

- [X] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/main/CONTRIBUTING.md) for this project.
- [X] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/main/CODE_OF_CONDUCT.md) that this project adheres to.
- [X] I have searched the [issue tracker](https://www.github.com/electron/electron/issues) for a feature request that matches the one I want to file, without success.

### Electron Version

16.0.2

### What operating system are you using?

macOS

### Operating System Version

macOS Monterrey 12.0.1

### What arch are you using?

arm64 (including Apple Silicon)

### Last Known Working Electron version

13

_No response_

### Expected Behavior

This configuration should produce a vibrant window:

```ts
new BrowserWindow({
    width: 800,
    height: 600,
    backgroundColor: undefined,
    vibrancy: "sidebar",
    titleBarStyle: "hidden",
    webPreferences: {
      preload: path.join(__dirname, 'preload.js')
    }
  })
```

### Actual Behavior

The window has a white background.

As of Electron 16.x vibrancy works if `backgroundColor` is not set at all, but not if it's explicitly set to `undefined`. As a consequence, if the background color is set to any value, it's impossible to unset it later.

### Testcase Gist URL

_No response_

### Additional Information

What's interesting is that this option check returns `true` if the background color is explicitly set to `undefined`:

https://github.com/electron/electron/blob/bd10b19b0cdc46cdbadb570af89305e64541b679/shell/browser/api/electron_api_browser_window.cc#L50

But this one returns `false`:

https://github.com/electron/electron/blob/bd10b19b0cdc46cdbadb570af89305e64541b679/shell/browser/native_window.cc#L208

shell/browser/api/electron_api_browser_window.cc
if (api_web_contents_->IsOffScreen())
    FocusOnWebView();
  else
    BaseWindow::Focus();
}
void BrowserWindow::Blur() {
  if (api_web_contents_->IsOffScreen())
    BlurWebView();
  else
    BaseWindow::Blur();
}
void BrowserWindow::SetBackgroundColor(const std::string& color_name) {
  BaseWindow::SetBackgroundColor(color_name);
  SkColor color = ParseHexColor(color_name);
  web_contents()->SetPageBaseBackgroundColor(color);
  auto* rwhv = web_contents()->GetRenderWidgetHostView();
  if (rwhv)
    rwhv->SetBackgroundColor(color);
  
  
  if (api_web_contents_) {
    auto* web_preferences =
        WebContentsPreferences::From(api_web_contents_->web_contents());
    if (web_preferences) {
      web_preferences->SetBackgroundColor(ParseHexColor(color_name));
    }
  }
}
void BrowserWindow::SetBrowserView(v8::Local<v8::Value> value) {