#13884 NncFluxData: Guard null grid/summaryView to fix crash during dynamic NNC transfer

ecl_file_get_restart_view can return null when a timestep has no restart
view, and the result was passed unchecked into ERT functions. Also added a
null guard for grid and summaryView at the entry of transferNncFluxData to
prevent a crash in ecl_nnc_geometry_alloc on null grid.

ApplicationLibCode/FileInterface/RifEclipseOutputFileTools.cpp

@@ -588,6 +588,8 @@ void RifEclipseOutputFileTools::transferNncFluxData( const ecl_grid_type*      g
                                                      std::vector<double>*      oilFlux,
                                                      std::vector<double>*      gasFlux )
 {
+    if ( !grid || !summaryView ) return;
+
     ecl_nnc_geometry_type* nnc_geo = ecl_nnc_geometry_alloc( grid );
     if ( nnc_geo )
     {