Fix regression of SMESH_TEST/Grids/smesh/imps6/G0
Fix regression of SMESH_TEST/Grids/smesh/imps6/G0

Clear _ImportData::_n2n if it's no more useful

FedoraScientific/salome-smesh,FedoraScientific/salome-smesh,FedoraScientific/salome-smesh,FedoraScientific/salome-smesh