mrtrix_gz: fixed overwrite of header offset on image load. issue #407
mrtrix_gz: fixed overwrite of header offset on image load. issue #407

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