app.execute() Fix erroneous error message
app.execute() Fix erroneous error message

If no scratch directory was generated, then upon an uncaught exception, the location of the scratch directory should not be printed to the terminal.

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