clicking hash link recorded in history twice

Describe the bug

When opening #anchor-a then click a link to #anchor-b, history newly records entries #anchor-a and #anchor-b though #anchor-a is previous location.

Therefore, hisotry looks like:

#anchor-a (initial view)
#anchor-b
#anchor-b (when clicked #anchor-b)
#anchor-c
#anchor-c (when clicked #anchor-c)
#anchor-d
#anchor-d (when clicked #anchor-d)
...

Disabling router by export const router = false; mitigate this issue, so that I think router has some issue around this.

Reproduction

https://stackblitz.com/edit/sveltekit-ivmzya?devtoolsheight=33&file=src/routes/index.svelte

Easily understand by following steps:

1. Open in New Window in Stackblitz
2. Clicking anchor links some times
3. Check a browser history, looks like:

(Also I notified null is oddly appealing on first clicking #anchor-b)

Logs

No response

System Info

# npx envinfo --system --binaries --browsers --npmPackages "{svelte,@sveltejs/*,vite}"
  System:
    OS: macOS 11.4
    CPU: (8) x64 Apple M1
    Memory: 24.88 MB / 16.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.13.2 - ~/.nodebrew/current/bin/node
    Yarn: 1.22.17 - ~/.nodebrew/current/bin/yarn
    npm: 8.1.2 - ~/.nodebrew/current/bin/npm
  Browsers:
    Firefox: 95.0
    Safari: 14.1.1
  npmPackages:
    @sveltejs/adapter-auto: next => 1.0.0-next.17
    @sveltejs/kit: next => 1.0.0-next.251
    svelte: ^3.46.3 => 3.46.3

### Severity

blocking an upgrade

### Additional Information

_No response_

[bluwy]

Yeah it does look like that this issue causes #3621. cc @vicky1999 in case you’re already working on a fix.

[benmccann]

This was fixed recently. The test has now been uncommented and passes:

https://github.com/sveltejs/kit/blob/a37f3b3de07304641cdae5d3686bfda6861b4489/packages/kit/test/apps/basics/test/test.js#L217