Fix typo in r31260

cmr=v1.8:ticket=trac:4470

This commit was SVN r31261.

The following SVN revision numbers were found above:
  r31260 --> open-mpi/ompi@69036437b7

The following Trac tickets were found above:
  Ticket 4470 --> https://svn.open-mpi.org/trac/ompi/ticket/4470

ompi/include/mpif-sentinels.h

@@ -54,7 +54,7 @@
 !     Ditto for MPI_STATUSES_IGNORE
       integer MPI_STATUSES_IGNORE(MPI_STATUS_SIZE, 1)
       integer MPI_UNWEIGHTED
-      integer MPI_WEIGHTS_NULL
+      integer MPI_WEIGHTS_EMPTY
 
       common/mpi_fortran_bottom/MPI_BOTTOM
       common/mpi_fortran_in_place/MPI_IN_PLACE