Crash when resizing a window running with XDG_SESSION_TYPE=x11 under KDE-Plasma/Wayland

### Checklist

- [x] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [x] For Python issues, I have tested with the [latest development wheel](https://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [x] I have checked the [release documentation](https://www.open3d.org/docs/release/) and the [latest documentation](https://www.open3d.org/docs/latest/) (for `main` branch).

### Describe the issue

Resizing the application window on a system running KDE-Plasma/Wayland with the setting `XDG_SESSION_TYPE=x11` causes an application crash.

### Steps to reproduce the bug

```python
export XDG_SESSION_TYPE=x11

python -c "import open3d as o3d; \
mesh = o3d.geometry.TriangleMesh.create_sphere(); \
mesh.compute_vertex_normals(); \
o3d.visualization.draw(mesh, raw_mode=True)"

# Resize the application window.
```

### Error message

```
terminate called after throwing an instance of 'utils::PostconditionPanic'
Aborted (core dumped) python -c "import open3d as o3d; mesh = o3d.geometry.TriangleMesh.create_sphere(); mesh.compute_vertex_normals(); o3d.visualization.draw(mesh, raw_mode=True)"
```

### Expected behavior

Obviously, resizing the application window should not crash the application. ;-)

### Open3D, Python and System information

```markdown
- Operating system: ArchLinux with KDE-Plasma/Wayland
- Python version: Python 3.14.3
- Open3D version: 0.19.0
- System architecture: x86
- Is this a remote workstation?: no
- How did you install Open3D?: pip
- Compiler version (if built from source):
```

### Additional information

Is it planned to natively support Wayland sometime in the near future?