BUG: sct_extract_metric: fixed bug related to saving text file
BUG: sct_extract_metric: fixed bug related to saving text file

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