Fix issue identified by Lisandro Dalcin regarding the lack

of support for NULL value in MPI_Type_set_attr.
Provides a fix for issue #1359.

ompi/mpi/c/type_set_attr.c

@@ -2,7 +2,7 @@
  * Copyright (c) 2004-2007 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
  *                         Corporation.  All rights reserved.
- * Copyright (c) 2004-2005 The University of Tennessee and The University
+ * Copyright (c) 2004-2016 The University of Tennessee and The University
  *                         of Tennessee Research Foundation.  All rights
  *                         reserved.
  * Copyright (c) 2004-2008 High Performance Computing Center Stuttgart,
@@ -52,8 +52,6 @@ int MPI_Type_set_attr (MPI_Datatype type,
         OMPI_ERR_INIT_FINALIZE(FUNC_NAME);
         if (NULL == type || MPI_DATATYPE_NULL == type) {
             return OMPI_ERRHANDLER_INVOKE(MPI_COMM_WORLD, MPI_ERR_TYPE, FUNC_NAME);
-    } else if (NULL == attribute_val) {
-      return OMPI_ERRHANDLER_INVOKE(MPI_COMM_WORLD, MPI_ERR_ARG, FUNC_NAME);
         }
     }