OPT: register_multimodal: added warning to ignore masking for centermass
OPT: register_multimodal: added warning to ignore masking for centermass

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