BUG: fixed #1053 related to straightening with low number of slices
BUG: fixed #1053 related to straightening with low number of slices

Former-commit-id: 421b18584cbf1d93fac1955d94897a39ca29f2d6 [formerly fb3f11723f81d4c0554f35cc86d0188d7aa5bb92]
Former-commit-id: 9e29e09eaeaa0ff7ff96b7100d2ea98e7529b7aa
Former-commit-id: fa519f5f07e721270b0365055f206234d20f36bf
Former-commit-id: 38073f85e2ef607c6354d0c813927a91a7f82dfe
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox