sct_straighten_spinalcord: some clean-up while troubleshooting remaining issue
sct_straighten_spinalcord: some clean-up while troubleshooting remaining issue


Former-commit-id: fd7878dd17739db208e2d8bc6c5fb5ffd88f91e5
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox