It actually does, using JavaScript:
<p class="err-content">This web server is running in SSL mode. Try the URL <a href='https://rpxy.digicard.net:10000/'>https://rpxy.digicard.net:10000/</a> instead.<script>if (location.protocol != 'https:') { location.protocol = 'https:';}</script></p>
I can't log in obviously, but the login page seems to be just fine. Maybe your Webmin has trouble with mixed content? Check your Chromes developer toolbars console to see more info.