Make ID.Str() handle nil ids correctly
Make ID.Str() handle nil ids correctly

byo/restic,ar-jan/restic,middelink/restic,rakoo/restic,fawick/restic,fawick/restic,ckemper67/restic,kurin/restic,jayme-github/restic,middelink/restic,howeyc/restic,jayme-github/restic,byo/restic,rakoo/restic,arithmetric/restic,intfrr/restic,bchapuis/restic,mappu/restic,klauspost/restic,ar-jan/restic,pombredanne/restic,stuertz/restic,restic/restic,restic/restic,stuertz/restic,episource/restic,kurin/restic