ros2 param dump should handle empty list as exception. (backport #881)

[mergify]

This is an automatic backport of pull request #881 done by Mergify.
Cherry-pick of d3cfbd7 has failed:

On branch mergify/bp/humble/pr-881
Your branch is up to date with 'origin/humble'.

You are currently cherry-picking commit d3cfbd7.
  (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:   ros2param/ros2param/verb/dump.py

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

---

Mergify commands and options

More conditions and actions can be found in the documentation.

You can also trigger Mergify actions by commenting on this pull request:

• @Mergifyio refresh will re-evaluate the rules
• @Mergifyio rebase will rebase this PR on its base branch
• @Mergifyio update will merge the base branch into this PR
• @Mergifyio backport <destination> will backport this PR on <destination> branch

Additionally, on Mergify dashboard you can:

• look at your merge queues
• generate the Mergify configuration with the config editor.

Finally, you can contact us on https://mergify.com

[fujitatomoya]

okay, humble does not have this issue (does not use zip method), it returns '# Parameter not set' string and set it into the dictionary with parameter name. it shows, parameter_name: # Parameter not set.

besides, we cannot backport ros2/rclpy#1216 to humble because it breaks the user space, that means this return '# Parameter not set' situation would happen even with statically typing parameter without default value. instead of modifying and changing behavior to handle this '# Parameter not set' case with exception, probably it is better to keep the current behavior as humble.

[fujitatomoya]

i will go ahead to close this, see details for #883 (comment)