sct_apply_transfo: complain if warping field isn't suitable for use
sct_apply_transfo: complain if warping field isn't suitable for use

... to avoid silent failure


Former-commit-id: 2edd5da33dce547acd065d7997b5c8951902c196
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox