I've tested that patch and with libxml 2.12.3 I have pytaest failing unit

+ PYTHONPATH=/home/tkloczko/rpmbuild/BUILDROOT/python-beautifulsoup4-4.12.2-6.fc35.x86_64/usr/lib64/python3.8/site-packages:/home/tkloczko/rpmbuild/BUILDROOT/python-beautifulsoup4-4.12.2-6.
+ /usr/bin/pytest -ra -m 'not network'
============================= test session starts ==============================
platform linux -- Python 3.8.18, pytest-7.4.3, pluggy-1.3.0
rootdir: /home/tkloczko/rpmbuild/BUILD/beautifulsoup4-4.12.2
collected 656 items

bs4/tests/test_builder.py .....                                          [  0%]
bs4/tests/test_builder_registry.py ...........                           [  2%]
bs4/tests/test_css.py .................................................. [ 10%]
..........                                                               [ 11%]
bs4/tests/test_dammit.py ..................................              [ 16%]
bs4/tests/test_element.py .....                                          [ 17%]
bs4/tests/test_formatter.py ..............                               [ 19%]
bs4/tests/test_fuzz.py .....ssssss                                       [ 21%]
bs4/tests/test_html5lib.py ............................................. [ 28%]
......................................                                   [ 33%]
bs4/tests/test_htmlparser.py ........................................... [ 40%]
...........F....................                                         [ 45%]
bs4/tests/test_lxml.py ................................................. [ 52%]
....................................................                     [ 60%]
bs4/tests/test_navigablestring.py ........                               [ 62%]
bs4/tests/test_pageelement.py ....................................       [ 67%]
bs4/tests/test_soup.py ................................................. [ 75%]
.........                                                                [ 76%]
bs4/tests/test_tag.py .......................                            [ 79%]
bs4/tests/test_tree.py ................................................. [ 87%]
........................................................................ [ 98%]
...........                                                              [100%]

=================================== FAILURES ===================================
_____ TestHTMLParserTreeBuilder.test_smart_quotes_converted_on_the_way_in ______

self = <bs4.tests.test_htmlparser.TestHTMLParserTreeBuilder object at 0x7f1aa6965c40>

    def test_smart_quotes_converted_on_the_way_in(self):
        # Microsoft smart quotes are converted to Unicode characters during
        # parsing.
        quote = b"<p>\x91Foo\x92</p>"
        soup = self.soup(quote)
>       assert soup.p.string == "\N{LEFT SINGLE QUOTATION MARK}Foo\N{RIGHT SINGLE QUOTATION MARK}"
E       AttributeError: 'NoneType' object has no attribute 'string'

bs4/tests/__init__.py:808: AttributeError
=========================== short test summary info ============================
SKIPPED [6] bs4/tests/test_fuzz.py:60: html5lib problems
FAILED bs4/tests/test_htmlparser.py::TestHTMLParserTreeBuilder::test_smart_quotes_converted_on_the_way_in
=================== 1 failed, 649 passed, 6 skipped in 4.23s ===================