BUG: fixed bug with CSF segmentation. Fixed #674 and #242
BUG: fixed bug with CSF segmentation. Fixed #674 and #242

3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox