Cannot close object, library is destroyed. This may cause a memory leak!

### Bug
There is a pdf file with color background, a PPTX converted to PDF.

Whether all bells and whistles enabled in PDF pipeline options or not, the message/error (in the title) is the same. What does that mean? And how can I fix it?

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### Steps to reproduce
Unfortunately, I can't share the file to test.
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### Docling version
2025-10-30 09:19:50,742 - INFO - Loading plugin 'docling_defaults'
2025-10-30 09:19:50,744 - INFO - Registered ocr engines: ['auto', 'easyocr', 'ocrmac', 'rapidocr', 'tesserocr', 'tesseract']
Docling version: 2.58.0
Docling Core version: 2.49.0
Docling IBM Models version: 3.10.2
Docling Parse version: 4.7.0
Python: cpython-312 (3.12.12)
Platform: Linux-6.6.87.2-microsoft-standard-WSL2-x86_64-with-glibc2.39