AttributeError: 'NoneType' object has no attribute 'get_object'

[DL6ER]

See #1269 for further details, this reports another issue I've come accross.

Environment

Which environment were you using when you encountered the problem?

$ python -m platform
Linux-5.4.0-122-generic-x86_64-with-glibc2.29

$ python -c "import PyPDF2;print(PyPDF2.__version__)"
2.10.3

Code + PDF

This is a minimal, complete example that shows the issue:

import PyPDF2
with open("Segmentation & Activation Lab.pdf", "rb") as f:
  pdfreader = PyPDF2.PdfFileReader(f, strict=False)
  full_content = " ".join([page.extractText() for page in pdfreader.pages])

PDF used above: Segmentation & Activation Lab.pdf

Traceback

This is the complete Traceback I see:

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/dist-packages/PyPDF2/_page.py", line 1538, in extractText
    return self.extract_text()
  File "/usr/local/lib/python3.8/dist-packages/PyPDF2/_page.py", line 1510, in extract_text
    return self._extract_text(
  File "/usr/local/lib/python3.8/dist-packages/PyPDF2/_page.py", line 1146, in _extract_text
    cmaps[f] = build_char_map(f, space_width, obj)
  File "/usr/local/lib/python3.8/dist-packages/PyPDF2/_cmap.py", line 21, in build_char_map
    encoding, space_code = parse_encoding(ft, space_code)
  File "/usr/local/lib/python3.8/dist-packages/PyPDF2/_cmap.py", line 124, in parse_encoding
    enc: Union(str, DictionaryObject) = ft["/Encoding"].get_object()  # type: ignore
AttributeError: 'NoneType' object has no attribute 'get_object'

The PDF can be read using a normal PDF viewer and the PDF even comes from Adobe.

Another example:

• Day 4 - Segmentation & Activation.pdf

[pubpub-zz]

This file uses a /XRefStm entry that seems not be be processed currently. Work in progress