SuperFrameFragment.getTimeslotOffset() tests getIISCH1().isValid() twice,
so the second I-ISCH is never consulted and a fragment whose first I-ISCH
does not decode is descrambled at timeslot offset 0. On a weak signal
the first I-ISCH fails on almost half of the fragments, and two of every
three of those are then descrambled with the wrong phase. Test I-ISCH 2
as the surrounding code intends (isFinalFragment() already does).
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>