mkUniqueOutPaths used to produce empty paths for dummy packages, this
version strips those out. This does not affect `pkgList.bin` at all, but
`pkgList.nonbin` is affected, so this is not exactly a refactoring. It
should not harm to have a cleaner `paths`.

Also, original comment said "here we deal with those dummy packages
needed for hyphenation filtering". This doesn't seem to be true, the
packages that were really filtered are actually metapackages that
represent collections. I also could not find any dummy packages even in
the originally committed version.

Initial language.{dat,def} configuration files provided by
`texlive.hyphen-base` may declare languages that were not part of the
combined packages. Those are filtered out by a sed script that had few
problems:

1) The sed script was generated from a list of potentially non-unique
packages. Every repetition of a select and print clause would produce a
copy of a language declaration in the output file. This became a problem
for update to the 2018-final, the fmtutil would crash from too much
German hyphenation.
2) The select clauses were ambiguous: both '^% from hyphen' and
'^% from hyphen-welsh' will match a line 'from hyphen-welsh'.

Biber 2.12 is for biblatex 3.12.