BUG: detect_vertebral_levels: fixed bug on sct_testing_data
BUG: detect_vertebral_levels: fixed bug on sct_testing_data

Former-commit-id: 10504082480ff85f8ee582e3a39e57e1aaa3d947 [formerly fd6a2e9a31a2622a2de3b491710a4aac02264ee2]
Former-commit-id: ff62400b74fab3f45de3ba56df714813746fb283
Former-commit-id: cd22f72c1e04c84ca8ef04decae754e09e1536b3
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox