address warning: statement with no effect. (backport #559)

[mergify]

Description

see https://ci.ros2.org/job/ci_linux-aarch64/21795/clang-tidy/folder.-1643903456/source.270fa858-97ec-4b07-9c86-ec11c84b9370/#478

--- stderr: rcutils                                                            
In file included from /root/ros2_ws/colcon_ws/src/ros2/rcutils/src/filesystem.c:42:
/root/ros2_ws/colcon_ws/src/ros2/rcutils/src/filesystem.c: In function ‘rcutils_dir_iter_next’:
/root/ros2_ws/colcon_ws/src/ros2/rcutils/src/filesystem.c:478:67: warning: statement with no effect [-Wunused-value]
  478 |   RCUTILS_CHECK_FOR_NULL_WITH_MSG(iter->state, "iter is invalid", false);
      |                                                                   ^~~~~
/root/ros2_ws/colcon_ws/src/ros2/rcutils/include/rcutils/error_handling.h:215:7: note: in definition of macro ‘RCUTILS_CHECK_FOR_NULL_WITH_MSG’
  215 |       error_statement; \
      |       ^~~~~~~~~~~~~~~
---

Fixes # (issue)

Is this user-facing behavior change?

No

Did you use Generative AI?

No

Additional Information

we need to backport this fix to all downstream branches.

---

This is an automatic backport of pull request #559 done by [Mergify](https://mergify.com).

[fujitatomoya]

Pulls: #561
Gist: https://gist.githubusercontent.com/fujitatomoya/9c2df8970b8a94312967535bea67c9f1/raw/3fac8c999c5157fe312dbf7e7f12e20fadfd67c1/ros2.repos
BUILD args: --packages-above-and-dependencies rctils
TEST args: --packages-above rctils
ROS Distro: kilted
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/19224

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[ahcorde]

Pulls: #561
Gist: https://gist.githubusercontent.com/ahcorde/3e2c0e241048d32707a019c1671e0315/raw/3fac8c999c5157fe312dbf7e7f12e20fadfd67c1/ros2.repos
BUILD args: --packages-above-and-dependencies rcutils
TEST args: --packages-above rcutils
ROS Distro: kilted
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/19235

• Linux
• Linux-aarch64
• Linux-rhel
• Windows