XSLT if sentence

I have this XSLT file:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
	<ul>
	<xsl:for-each select="opml/body/outline">
		<li id="{@url}"><a href="/{@url}"><xsl:value-of select="@title" /></a></li>
	</xsl:for-each>
	</ul>
</xsl:template>
</xsl:stylesheet>

I'd like an if sentence before the <ul> tag, so that only if there are
any outline rows, the <ul> tag will be there.

I hope you understand my poor english.

Thanks,
Jacob