BUG: fixed a bug with t2star segmentation
BUG: fixed a bug with t2star segmentation

Former-commit-id: 156cd520d894c15ac30227980237e1957cc35c11
Former-commit-id: 2a3730807b54478b7be19fee348ccdbcbb21a87c
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox