Make read more working with comments in teaser

Read more was working fine until I installed the trackback module. The trackback module appends the following string to the teaser:

<!--
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:trackback="http://madskills.com/public/xml/rss/module/trackback/">
<rdf:Description rdf:about="http://cyber4kids/node/432" dc:identifier="http://cyber4kids/node/432" dc:title="Der Ferienpass ist da!" trackback:ping="http://cyber4kids/trackback/432" />
</rdf:RDF>
-->

As you can see the teaser is now ending by a comment. Therefore the function ed_readmore_link_place won't recognize the end of the teaser text. To fix this we need to check the teaser without the appended html comment. So I inserted the following condition in the ed_readmore_link_place function, this calls the ed_readmore_link_place function recursively without the last html comment:

    else if (preg_match('%\s*<\!--.*?--\>\s*$%is', $teaser, $match, PREG_OFFSET_CAPTURE)) {
      $teaser = ed_readmore_link_place(substr($teaser, 0, $match[0][1]), $node, $display) . $match[0][0];
    }

I also have attached a patch which contains this solution. I'm not sure about the efficiency/performance of the none-greedy regular expression I used ... please review the expression.