docs: update #each to reflect support for null and undefined

[RazinShafayet2007]

Description

Updated the #each block documentation to explicitly state that null and undefined are supported and treated as empty loops (skipping the block).

Related Issue

Fixes #17337

Motivation

The current docs suggest using Array.from, which throws an error on null or undefined. This update clarifies that defensive coding like items ?? [] is no longer necessary in Svelte 5.

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Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

[changeset-bot]

⚠️ No Changeset found

Latest commit: e2f2933

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-svelte-17339-svelte.vercel.app/

[Rich-Harris]

thank you

[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@17339