BUG: fmri_compute_tsnr: fixed 1244 (#1245)
BUG: fmri_compute_tsnr: fixed 1244 (#1245)



Former-commit-id: 42522ed71225a9d305d24b9075be96e0637e7dd8
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox