[PATCH follow-up] obsfate: fix obsfate_printer with empty date list

[Yuya Nishihara]

On Wed, 18 Oct 2017 16:35:02 +0200, Boris Feld wrote:
> # HG changeset patch
> # User Boris Feld <boris.feld at octobus.net>
> # Date 1508333931 -7200
> #      Wed Oct 18 15:38:51 2017 +0200
> # Node ID 328ec528162a716ef61877de1982860b67973afa
> # Parent  962f7df21a73f044d171fee9c237d0c5062ae317
> # EXP-Topic elite-mink
> # Available At https://bitbucket.org/octobus/mercurial-devel/
> #              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r 328ec528162a
> obsfate: fix obsfate_printer with empty date list
> 
> When the list of dates is empty, `min` and `max` would raises a ValueError.
> Protect against this case by checking that the date list is not empty.
> 
> I didn't add a test because I couldn't find a reproducing test case.

This happens if markers list is empty. Perhaps a weird case of prune?