bugfix: incorrect idxstats for the last seq
bugfix: incorrect idxstats for the last seq

Again, this bug is caused by 3rd-party code for the sorting order checking.

AngieHinrichs/samtabix,AngieHinrichs/samtabix,AngieHinrichs/samtabix,lh3/samtools,lh3/samtools,lh3/samtools,AngieHinrichs/samtabix,AngieHinrichs/samtabix