BUG: fixed edge's effect when using hanging window in sct_straighten_spinalcord
BUG: fixed edge's effect when using hanging window in sct_straighten_spinalcord

Former-commit-id: b0f49194271034218029723c5a7d99ccc317f61d
Former-commit-id: a8a6da1188bdb123bacd68ffc39305b09288ea02
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox