Dated user CSS with <style> tags cannot be parsed #425

At one point the original user CSS in the Site#stylesheet skin contained <style> tags:

<style type='text/css'>
<!--
…
//-->
</style>

In the meantime, the user CSS is loaded via action as external stylesheet (text/css) – and this structure cannot be parsed by the Less parser.

The error is visible in the main.css file at the client:

/**
LESS parser got exception when rendering custom CSS.
 error in line  column  of undefined: org.lesscss.LessException: ParseError: Unrecognised input in /tmp/tmp17820753273792177474less.tmp on line 702, column 1:
701 
702 <style type="text/css">
703 <!--