free(): invalid pointer crash when loading PDF with docling_parse (v4.0.1 / CPU / Python 3.12)

Title:
free(): invalid pointer crash when loading PDF with docling_parse (v4.0.1 / CPU / Python 3.12)

Body:

Hey Docling team,

I’m consistently running into a fatal crash when using docling_parse (version 4.0.1) with Python 3.12 and the CPU-only version of PyTorch (no CUDA).

The crash happens during document parsing — specifically when calling _load_document() from pdf_parser.py in doclin_parse version 4.0.1. Here's the error:

```bash
free(): invalid pointer
Fatal Python error: Aborted
```

And this is the relevant part of the stacktrace:

File ".../docling_parse/pdf_parser.py", line 489 in _load_document
File ".../docling_parse/pdf_parser.py", line 455 in load
...

I’ve confirmed the following:

PyTorch is installed correctly as 2.6.0+cpu, no CUDA present

Python version is 3.12.3

No crash when importing torch or pdfminer.six separately

Downgrading docling_parse to 4.0.0 and 3.4.0 does not resolve the issue

The crash happens inside your library, likely due to a native extension or unsafe memory access

Would really appreciate it if you could look into this — especially since it completely breaks CPU-only setups. Let me know if you need more info to reproduce.

Thanks.