ompi: silence CID 1343322

ompi/mpi/c/alltoall.c

@@ -93,6 +93,7 @@ int MPI_Alltoall(const void *sendbuf, int sendcount, MPI_Datatype sendtype,
     }
 
     if (! OMPI_COMM_IS_INTER(comm)) {
+        ompi_datatype_type_size(recvtype, &recvtype_size);
         if( (0 == recvcount) || (0 == recvtype_size) ) {
             return MPI_SUCCESS;
         }