Small fix to dwi2fod to ensure non-masks voxel are initalised to zero
Small fix to dwi2fod to ensure non-masks voxel are initalised to zero

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