fix: input checkbox value should always be included even when null

[ghiscoding]

• last version refactoring removed all empty props & attributes when creating DOM element but we should never remove input value prop even when it is null or empty

[github-actions]

🎭 Playwright Summary - Success 🎉

Playwright Report

[email protected] test:e2e /home/runner/work/multiple-select-vanilla/multiple-select-vanilla
playwright test --config playwright/playwright.config.ts

Running 69 tests using 1 worker
·····································································
69 passed (2.0m)