Fix warning

src/drivers/cpu/driver_cpu.c

@@ -378,7 +378,10 @@ int _starpu_cpu_driver_run_once(struct _starpu_worker *cpu_worker)
 	cpu_worker->current_rank = rank;
 
 	if (rank == 0)
-		_starpu_fetch_task_input(task, j, 1);
+	{
+		res = _starpu_fetch_task_input(task, j, 1);
+		STARPU_ASSERT(res == 0);
+	}
 	else
 		return _starpu_cpu_driver_execute_task(cpu_worker, task, j);
 	return 0;