Fix Overview crash on hrefless README anchors

[jo-duchan]

Summary

Fixes #2670. The package Overview page throws a client-side exception and renders the error page when a README contains a hrefless anchor (e.g. <a name="section"></a>).

Cause

In MarkdownRenderer.tsx, the a handler starts with:

if (props.href.startsWith('#')) {

rehype-raw parses <a name="..."> into an anchor node with no href, so props.href is undefined and .startsWith() throws, which takes down the whole Overview render.

Fix

if (props.href?.startsWith('#')) {

The handler already ends with a return <span>{props.children}</span> fallback, so with optional chaining a hrefless anchor falls through to that fallback instead of crashing. One-character change, no behavior change for anchors that have an href.

Reproduction

Live example before the fix: https://reactnative.directory/package/tapflow (Overview tab crashes; Code / Versions / Score are fine). Console:

TypeError: Cannot read properties of undefined (reading 'startsWith')
  at MarkdownRenderer.tsx:90

Also reproduced the parse with a standard remark -> remark-rehype (allowDangerousHtml) -> rehype-raw pipeline: a <a name> anchor yields one <a> node without an href, which is what hits the unguarded .startsWith.

[Simek]

Thanks for the bug report and fix! 👍

I have fixed it once in the past, but then broke this again when adding support for hash links. 😅 Need to find a way to correctly extract types for custom elements in @m2d/react-markdown/client markdown renderer, so we can avoid similar issues in the future.

[jo-duchan]

Thanks for the quick merge! Makes sense — those custom-element types are tricky. Glad the optional-chaining fallback helps in the meantime.