ValueError: max() arg is an empty sequence

[smcgivern]

Describe the bug
When given a relative path and absolute path, sqlfmt fails with:

$ sqlfmt data/models/foo.sql /Users/smcgivern/Code/linear-app/data/models/bar.sql
Traceback (most recent call last):
  File "/Users/smcgivern/.asdf/installs/python/3.11.3/bin/sqlfmt", line 8, in <module>
    sys.exit(sqlfmt())
             ^^^^^^^^
  File "/Users/smcgivern/.asdf/installs/python/3.11.3/lib/python3.11/site-packages/click/core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/smcgivern/.asdf/installs/python/3.11.3/lib/python3.11/site-packages/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "/Users/smcgivern/.asdf/installs/python/3.11.3/lib/python3.11/site-packages/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/smcgivern/.asdf/installs/python/3.11.3/lib/python3.11/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/smcgivern/.asdf/installs/python/3.11.3/lib/python3.11/site-packages/click/decorators.py", line 26, in new_func
    return f(get_current_context(), *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/smcgivern/.asdf/installs/python/3.11.3/lib/python3.11/site-packages/sqlfmt/cli.py", line 176, in sqlfmt
    config = load_config_file(files)
             ^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/smcgivern/.asdf/installs/python/3.11.3/lib/python3.11/site-packages/sqlfmt/config.py", line 23, in load_config_file
    common_parents = _get_common_parents(files)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/smcgivern/.asdf/installs/python/3.11.3/lib/python3.11/site-packages/sqlfmt/config.py", line 55, in _get_common_parents
    root_dir = max(common_parents, key=lambda p: p.parts)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: max() arg is an empty sequence

To Reproduce

Run sqlfmt with two paths, one relative and one absolute.

Expected behavior

It doesn't crash 🙂 More precisely, it converts the relative path to an absolute one first.

Actual behavior

Crashes as above.

Additional context
What is the output of sqlfmt --version?

$ sqlfmt --version
sqlfmt, version 0.18.1