fixed wrong index (issue 1882) (#1882)
fixed wrong index (issue 1882) (#1882)



Former-commit-id: 067e203c96a099cefc79b453048857f5703e2fbd
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox