dwipreproc: Fix generation of text files for applytopup
dwipreproc: Fix generation of text files for applytopup

MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3