Removed warning (backport #312)

[mergify]

New warning on packaging_linux-rhel https://ci.ros2.org/view/packaging/job/packaging_linux-rhel/1934/clang/new/

---

This is an automatic backport of pull request #312 done by Mergify.

[mergify]

Cherry-pick of d909f9b has failed:

On branch mergify/bp/jazzy/pr-312
Your branch is up to date with 'origin/jazzy'.

You are currently cherry-picking commit d909f9b.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   image_transport/src/publisher.cpp

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[ahcorde]

We'll hold this for Jazzy patch release 1.

Requires #310

[ahcorde]

• Linux
• Linux-aarch64
• Windows