`permalink: undefined` in `mardown` settings disables Outline

[shellscape]

Describe the bug

When setting:

  markdown: {
    anchor: {
      permalink: undefined
    }
  },

The permalinks on header elements are successfully hidden, but that also disables the scroll-tracking for the "On This Page" outline sidebar as well.

Reproduction

I was able to reproduce this on the boilerplate project by applying the setting above to the config.

Expected behavior

Permalink symbols correctly hidden, outline continues to function.

System Info

MacOS Ventura
Vitepress@latest
Node v18

(envinfo hangs on an M2)

Additional context

No response

Validations

• Check if you're on the latest VitePress version.
• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.

[brc-dd]

Use something like this via CSS for now:

.vp-doc .header-anchor {
  visibility: hidden;
}

The current implementation relies on those anchors to be present. Will see what we can do.

[shellscape]

that's what I'm doing. display: none: also causes the same issue as reported.