BUG: msct_register: fixed bug with rigid transformation
BUG: msct_register: fixed bug with rigid transformation

Former-commit-id: 5c4927098dcf75c5603f59a744cb047121c32823
Former-commit-id: aea0a7abdd537f776ccd6a4a8f45d1018767eda2
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox