Fix issue reading matrix files, introduced by 7f97a84d
Fix issue reading matrix files, introduced by 7f97a84d

Every space was interpreted as a separator, causing the matrix loader to
try to parse additional empty entries.

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