BUG: when user does not have vertebral_levels.nii.gz, script crashes. Now coming back to previous commit. Needs to be fixed in the future.
BUG: when user does not have vertebral_levels.nii.gz, script crashes. Now coming back to previous commit. Needs to be fixed in the future.

3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox