Typo3 URI problem

What is the synopsis?
I used mc_googlesitemap (version 0.4.2; which seemed buggy). Google Webmaster Tools accepted the URI in the sitemap. I quick fixed the problem in the extension mc_googlesitemap (URI still persists in google site search).

You could ask for my fix but I would be rather you use another extension! Anyhow I understand if you have a problem. I am sure you know how to contact me if you are not a bot.

What was wrong?

http://www.DOMAIN.TLD/http://www.DOMAIN.TLD/ does not cause an error.
http://www.DOMAIN.TLD/http://www.DOMAIN.TLD/http://www.DOMAIN.TLD/ does.

it’s even this which triggers it: http://www.DOMAIN.TLD/X://X

And this shows a blank page:

http://www.DOMAIN.TLD/X:/X
http://www.DOMAIN.TLD/X:X
http://www.DOMAIN.TLD/X:

What is my typo 3 version?
It is 4.5.2 and my realurl setup is at pastebin.com

What is my temporary workaround?
For now I put this in my .htaccess and I know it does not cover all cases mentioned above:

RewriteCond %{REQUEST_URI} ^(/http://.*|/https://.*)
RewriteRule ^(.*)$ http://%{HTTP_HOST}/page-not-found.html [R=301,L,E=nolog:1]