BUG: fixed bug with index and cropping in sct_straighten_spinalcord
BUG: fixed bug with index and cropping in sct_straighten_spinalcord

Former-commit-id: 0551f6ced33b8ca6b04a4674ee3a49e50cf6011f [formerly 7df29170d399ac4c043159daf6a7a0f22005e668]
Former-commit-id: 1e25ecca8a05b6d2ae767fe3ad1e677095141868
Former-commit-id: 9ccc5290a4f226fc286097d41515ea05e7521e98
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox