snap: fix case when snap list is empty

[russoz]

SUMMARY

Exception was being raised when snap list was empty.

Fixes #7120

ISSUE TYPE

• Bugfix Pull Request
• Test Pull Request

COMPONENT NAME

snap

[ansibullbot]

cc @angristan @vcarceler
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[felixfontein]

Thanks, looks good! Can you please add a changelog fragment? :)

[patchback]

Backport to stable-6: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply 33998a5 on top of patchback/backports/stable-6/33998a5b707a9797f3ba594571ff77744ad0a764/pr-7124

Backporting merged PR #7124 into main

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/ansible-collections/community.general.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/stable-6/33998a5b707a9797f3ba594571ff77744ad0a764/pr-7124 upstream/stable-6

4. Now, cherry-pick PR snap: fix case when snap list is empty #7124 contents into that branch:

   $ git cherry-pick -x 33998a5b707a9797f3ba594571ff77744ad0a764

   If it'll yell at you with something like fatal: Commit 33998a5b707a9797f3ba594571ff77744ad0a764 is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x 33998a5b707a9797f3ba594571ff77744ad0a764

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR snap: fix case when snap list is empty #7124 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/stable-6/33998a5b707a9797f3ba594571ff77744ad0a764/pr-7124

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[patchback]

Backport to stable-7: 💚 backport PR created

✅ Backport PR branch: patchback/backports/stable-7/33998a5b707a9797f3ba594571ff77744ad0a764/pr-7124

Backported as #7128

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[felixfontein]

@russoz thanks for fixing this!