BUG: fixed small bug on sct_label_utils
BUG: fixed small bug on sct_label_utils

Former-commit-id: b1a78eab3a384febd5c9f44e5b9408aeb4890217 [formerly 9f77958da432ba1f7530f7d64e068c2eb7a44551]
Former-commit-id: b54fcfa13800d7229e6fe16557296dbaf7f6bbef
Former-commit-id: 72a3d32f1b889d15fc2b183ac32888e546fce0ec
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox