fix(FormField): resolve minor accessibility and rendering issues

[ThiloHettmer]

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This PR fixes two minor issues. First one is that in the Formfield component the help text has no id, and the Input component references it through useFormfield by its aria-describedby. Second issue is that the aria-describedby is added even if no help text is provided to the Formfield component.

[pkg-pr-new]

npm i https://pkg.pr.new/@nuxt/ui@4515

commit: 50d348d

[romhml]

Thanks @ThiloHettmer :)

Could you add a few test cases to lock these in? https://github.com/nuxt/ui/blob/v3/test/components/FormField.spec.ts#L108

[ThiloHettmer]

Hi @romhml :) I have added 2 tests