rediraffecheckdiff fails when using a redirect dict

[doismellburning]

Running rediraffecheckdiff on a Sphinx setup where rediraffe_redirects is set to an empty dict in conf.py results in an AttributeError: 'NoneType' object has no attribute 'open' that looks to come from rediraffe assuming rediraffe_redirects is a file (despite documentation and source indicating that both files and dicts should be supported)

Specifically:

$ grep --after-context=1 ^rediraffe source/conf.py 
rediraffe_branch = "main"
rediraffe_redirects = {
}

$ pipenv run sphinx-build -b=rediraffecheckdiff source build -W --keep-going -E -v
Running Sphinx v7.2.6
Initializing Spelling Checker 8.0.0
locale_dir /Users/doismellburning/git/tech-docs/source/locales/en/LC_MESSAGES does not exist

Traceback (most recent call last):
  File "/Users/doismellburning/.local/share/virtualenvs/tech-docs-26HPyE37/lib/python3.9/site-packages/sphinx/cmd/build.py", line 293, in build_main
    app = Sphinx(args.sourcedir, args.confdir, args.outputdir,
  File "/Users/doismellburning/.local/share/virtualenvs/tech-docs-26HPyE37/lib/python3.9/site-packages/sphinx/application.py", line 272, in __init__
    self._init_builder()
  File "/Users/doismellburning/.local/share/virtualenvs/tech-docs-26HPyE37/lib/python3.9/site-packages/sphinx/application.py", line 342, in _init_builder
    self.builder.init()
  File "/Users/doismellburning/.local/share/virtualenvs/tech-docs-26HPyE37/lib/python3.9/site-packages/sphinxext/rediraffe.py", line 386, in init
    with redirects_path.open("a") as redirects_file:
AttributeError: 'NoneType' object has no attribute 'open'
[snip]

It looks like there's logic at https://github.com/wpilibsuite/sphinxext-rediraffe/blob/v0.2.7/sphinxext/rediraffe.py#L301-L302 to check for if the config is a dict, but then later https://github.com/wpilibsuite/sphinxext-rediraffe/blob/v0.2.7/sphinxext/rediraffe.py#L386 just assumes there's a file to be opened