Fix version output (single git repo without group case)

[Tibshot]

When trying to get backup versions in single repo without groups, I was getting 'Versions not found'.

[ytti]

This is probably mistake in somewhere else in the code. I think we should guarantee group to be nil or false if we don't have group. Why is it empty string? Can we fix it in the earlier point?

[mortzu]

Any news on this?