oixy: treat z as in oi

pub/lib/opr.cpp

@@ -376,8 +376,8 @@ void NOperate::IntXY( string mode )
                 sout->push_xy( fin->VS(j)->y[icolx],
                                fin->VS(j)->y[icoly] );
             sout->z = fin->VS(j)->z;
-            if ( nz ) { // new spectrum if jump in any z values
-                if ( j+1 < fin->nJ() && fin->V[j+1]->z != fin->V[j]->z ) {
+            if ( nz>2 ) { // new spectrum if jump in other z value
+                if ( j+1<fin->nJ() && fin->V[j+1]->z[nz-2]->to_r() != fin->V[j]->z[nz-2]->to_r() ) {
                     fout->V.push_back( move(sout) );
                     sout = PSpec( new CSpec );
                 }