Catch case of nonexistent IRDB package root dir

[teutoburg]

As per #287 (comment)

[teutoburg]

Should be trivial, I'll merge...

[hugobuddel]

Thanks. Let's see tomorrow whether it worked!

[hugobuddel]

So close! https://github.com/AstarVienna/ScopeSim_Data/actions/runs/6715938272/job/18251458780

File /tmp/tmp.BV6rC3Nx40/ScopeSim/scopesim/utils.py:468, in _write_bug_report(stream)
    466 pkgs_path = Path(rc.__config__["!SIM.file.local_packages_path"])
    467 installed_pkgs = _get_all_irdb_pkgs(pkgs_path)
--> 468 maxkeylen = max(len(pkg.stem) for pkg in installed_pkgs)
    469 for pkg_path in installed_pkgs:
    470     pkg_ver = _get_irdb_pkg_version(pkg_path)

ValueError: max() arg is an empty sequence

perhaps

maxkeylen = max(len(pkg.stem) for pkg in installed_pkgs + [""])

or

maxkeylen = max(len(pkg.stem) for pkg in installed_pkgs) if installed_pkgs else 0

or maybe 1 if 0 is too short for some reason.

Now I wonder, are there programming languages where this would just work? That is, a good type system could infer that we're taking the maximum of the length of strings. And it seems feasible to somehow encode in a type system that the maximum of an empty list should be the lowest possible maximum, which in this case is definable as 0.

I was wondering because both the above solutions are ugly. However, writing this useless comment gave me the time to reflect, and there is a third option that is not ugly (in my eyes), because it comes closest to what I tried to convey above:

maxkeylen = max((len(pkg.stem) for pkg in installed_pkgs), default=0)