Added explicit null return to MRTRIX_APPLICATION macro to quieten warnings
Added explicit null return to MRTRIX_APPLICATION macro to quieten warnings

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