Summary

still part of https://github.com/langgenius/dify/pull/10921 when rules are empty will case in None bug, better is empty dict

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Screenshots

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[!IMPORTANT]
Please review the checklist below before submitting your pull request.

[ ] This change requires a documentation update, included: Dify Document
[x] I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
[x] I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
[x] I've updated the documentation accordingly.
[x] I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods