[18.0][FIX] hr_shift: reduce crash when missing data

[mathben]

last_plan can be False and default_vals can be empty
fix typo Self #25 (comment)

[mathben]

This pull request correct this crash.
First execution without demo data.

    week_number=default_vals["week_number"],
                ~~~~~~~~~~~~^^^^^^^^^^^^^^^
KeyError: 'week_number'

[david-banon-tecnativa]

LGTM, some minor comments

[mathben]

@david-banon-tecnativa Thanks for your reviews, I implement your proposition.

[david-banon-tecnativa]

Thanks, please force push again, CI failed but i don't think its related to the PR

[pedrobaeza]

I'm able to relaunch it, so I have done it. Let's see

[mathben]

The check pass after relaunch @pedrobaeza
Thanks

[OCA-git-bot]

This PR has the approved label and has been created more than 5 days ago. It should therefore be ready to merge by a maintainer (or a PSC member if the concerned addon has no declared maintainer). 🤖

[pedrobaeza]

/ocabot merge patch

[OCA-git-bot]

What a great day to merge this nice PR. Let's do it!
Prepared branch 18.0-ocabot-merge-pr-26-by-pedrobaeza-bump-patch, awaiting test results.

[OCA-git-bot]

Congratulations, your PR was merged at 6779953. Thanks a lot for contributing to OCA. ❤️