canonical() does not return correct value, if routes -> canonical is set

[AndeeZee]

If my page contains a specific entry for canonical route and the server url differs from that page, canonical returns a concatenated value, which breaks the sitemap and therefor other processes and plugins like seo-magic.

Example:

I have my page open with url:
https://my-url.tld

In my page.md, the following header is defined:

---

routes:
    canonical: https://www.my-url.tld
---

Because the prefixed www should be the canonical one.

In that case, the canonical() function returns a concatenated value of both:
https://my-url.tldhttps://www.my-url.tld

This will break further processes, relying on a correct sitemap.

Any help/fix appreciated! Thank you!