removed useless error

mpi/src/starpu_mpi_task_insert.c

@@ -811,10 +811,6 @@ void starpu_mpi_redux_data_prio_tree(MPI_Comm comm, starpu_data_handle_t data_ha
 	{
 		arity = nb_contrib;
 	}
-	if (arity < 2)
-	{
-		_STARPU_ERROR("StarPU can only operate an inter-node reduction on a tree with at least two nodes.\n");
-	}
 	_STARPU_MPI_DEBUG(5, "There is %d contributors\n", nb_contrib);
 	int contributors[nb_contrib];
 	int reducing_node;