[Bug] Crashing when z-order is topmost on MacOS

### Describe the bug

When you open a widget that has set their Z-order to Topmost Zebar will instantly crash without writing anything to errors.log on MacOS (Tahoe 26.2).

### Reproduction

1. Install latest version of zebar
2. Create a copy of the vanilla example
3. Set Z-order to topmost
4. Open

### Stack trace or error logs (if applicable)

```shell

```

### Version number

v3.1.1