Fix BufferLoader for negative offset
Fix BufferLoader for negative offset

jayme-github/restic,ckemper67/restic,byo/restic,stuertz/restic,arithmetric/restic,middelink/restic,kurin/restic,restic/restic,fawick/restic,kurin/restic,jayme-github/restic,stuertz/restic,byo/restic,ar-jan/restic,middelink/restic,ar-jan/restic,fawick/restic,restic/restic