BUG: fixed bug on vertebral levels
BUG: fixed bug on vertebral levels

Former-commit-id: 0328528c0fb6af83f1febeb728ffb1f4cb6f7653
Former-commit-id: 1b0cb950eae7a3c1802f16acf9df1de6306e44ca
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox