bug#21991: 'guix download' without arguments produces guile backtrace

[Ludovic Courtès]

Jan Synáček <jan.syna...@gmail.com> skribis:

> I guess it should just print an error or display usage.

Indeed.  Fixed in 71ae18e.  Commit 86cdfc4 fixes another source of
sloppiness in argument parsing.

Thank you!

Ludo’.