use reInit for field

src/Copy.cc

@@ -151,7 +151,7 @@ Copy(void *process)
                 }
               else
                 {
-                  field = FieldFactory::init(varList1[varID]);
+                  field = FieldFactory::reInit(field, varList1[varID]);
                   cdo_read_record(streamID1, field);
                   cdo_write_record(streamID2, field);
                 }