coverage extension crashes when module contents are not found

[aragilar]

Describe the bug

It appears if the coverage extension fails to find the module (or simply is empty, then it crashes because it divides by the number of objects in that module, which is 0.

Traceback (most recent call last):
  File "/home/aragilar/Projects/DC/dcldap/.tox/docs/lib/python3.11/site-packages/sphinx/cmd/build.py", line 298, in build_main
    app.build(args.force_all, args.filenames)
  File "/home/aragilar/Projects/DC/dcldap/.tox/docs/lib/python3.11/site-packages/sphinx/application.py", line 355, in build
    self.builder.build_update()
  File "/home/aragilar/Projects/DC/dcldap/.tox/docs/lib/python3.11/site-packages/sphinx/builders/__init__.py", line 290, in build_update
    self.build(['__all__'], to_build)
  File "/home/aragilar/Projects/DC/dcldap/.tox/docs/lib/python3.11/site-packages/sphinx/builders/__init__.py", line 363, in build
    self.write(docnames, list(updated_docnames), method)
  File "/home/aragilar/Projects/DC/dcldap/.tox/docs/lib/python3.11/site-packages/sphinx/ext/coverage.py", line 110, in write
    self.write_py_coverage()
  File "/home/aragilar/Projects/DC/dcldap/.tox/docs/lib/python3.11/site-packages/sphinx/ext/coverage.py", line 310, in write_py_coverage
    self._write_py_statistics(sys.stdout)
  File "/home/aragilar/Projects/DC/dcldap/.tox/docs/lib/python3.11/site-packages/sphinx/ext/coverage.py", line 295, in _write_py_statistics
    f'{100 * len(all_documented_objects) / len(all_objects):.2f}%',
       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
ZeroDivisionError: division by zero

How to Reproduce

Running the coverage builder on an empty project should reproduce this.

Environment Information

# Platform:         linux; (Linux-6.4.0-4-amd64-x86_64-with-glibc2.37)
# Sphinx version:   7.2.5
# Python version:   3.11.5 (CPython)
# Docutils version: 0.20.1
# Jinja2 version:   3.1.2
# Pygments version: 2.16.1

Sphinx extensions

# Loaded extensions:
#   sphinx.ext.mathjax (7.2.5)
#   alabaster (0.7.13)
#   sphinxcontrib.applehelp (1.0.7)
#   sphinxcontrib.devhelp (1.0.5)
#   sphinxcontrib.htmlhelp (2.0.4)
#   sphinxcontrib.serializinghtml (1.1.9)
#   sphinxcontrib.qthelp (1.0.6)
#   sphinx.ext.autodoc.preserve_defaults (7.2.5)
#   sphinx.ext.autodoc.type_comment (7.2.5)
#   sphinx.ext.autodoc.typehints (7.2.5)
#   sphinx.ext.autodoc (7.2.5)
#   sphinx.ext.doctest (7.2.5)
#   sphinx.ext.coverage (7.2.5)
#   sphinxcontrib.confluencebuilder (2.2.0)

Additional context

No response

[picnixz]

I think 31829a9 is meant to fix this (the PR hasn't landed yet because the bug was probably discovered only now).

cc @stephenfin

[stephenfin]

Yup, I found and fixed that as part of #11592. Feel free to pull that out into its own PR if needed.