Tradindexed should not use zero length files for empty groups

[Julien ÉLIE]

4. Stussy reports in <​news:gqh1ra$c58$1@aux.snarked.org> that INN makes zero length files for the traditional overview format but when the groups are empty, it is worthless. It uselessly consumes lots of inodes.

Russ Allbery writes that "there's no basic technical reason why that couldn't be done, but it simplified the code to not have to worry about that case, which is why it currently works the way it does."

However, it would be better not to reserve resources.