Sketcher/PartDesign: Pocket doesn't throw error when used on invalid sketch containing B-spline

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Problem description

Can't create pocket with this very specific sketch, I suspect it has to do with the bspline
[M12.FCStd.zip](https://github.com/FreeCAD/FreeCAD/files/12503994/M12.FCStd.zip)

https://github.com/FreeCAD/FreeCAD/assets/12400097/740968d3-318d-4f0e-94ac-64495c80dc9c

### Full version info

```shell
OS: Ubuntu Core 22 (ubuntu:GNOME/ubuntu)
Word size of FreeCAD: 64-bit
Version: 0.22.0dev.34091 (Git) Snap 758
Build type: Release
Branch: master
Hash: a2735416e1189566329b327d99f115ced7071b86
Python 3.10.12, Qt 5.15.10, Coin 4.0.0, Vtk 7.1.1, OCC 7.7.1
Locale: English/United States (en_US)
Installed mods:
* Help 1.0.3
```

### Subproject(s) affected?

Part Design, Sketcher

### Anything else?

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct

Open the attached M12.FCStd file from M12.FCStd.zip in FreeCAD and reproduce the Pocket operation using the invalid sketch containing a B-spline. Start by examining the Part Design and Sketcher behavior involved; done means the invalid sketch is rejected with a clear error when creating the Pocket.

Written by the indexing model from the issue text.