IndexError while processing a PDF file

### Bug

...

### Steps to reproduce
JUST RUNNING the code below in Google COLAB (or VSCODE):
from docling.document_converter import DocumentConverter

source = "LAB_CLINICAL_EXAMS.pdf"

converter = DocumentConverter()
result = converter.convert(source)
print(result.document.export_to_markdown())

...

### Docling version
FROM COLAB:
Docling version: 2.23.0
Docling Core version: 2.19.1
Docling IBM Models version: 3.3.2
Docling Parse version: 3.3.1
Python: cpython-311 (3.11.11)
Platform: Linux-6.1.85+-x86_64-with-glibc2.35

...

### Python version
Python from Google COLAB:
Python: cpython-311 (3.11.11)

...

ATTENTION:
PDF File is a sensitive file (not included), received for a Clinical Analysis Laboratory