Adding both a timer and subscription to the executor seems to cause error_loop() to run

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Hi all, I'm working with micro-ros and I'm trying to add in my script a timer and subscription, but always it cause an error in error_loop when it’s execued. It's posible to have them both in the same script?.

RCCHECK(rclc_executor_init(&executor, &support.context, 1, &allocator));

RCCHECK(rclc_executor_add_subscription(&executor, &subscriber, &msg_cmd_vel, &subscription_callback, ALWAYS));

RCCHECK(rclc_executor_add_timer(&executor, &timer));

Thank you for your help.