I created template that return teaserImage XML and that is protected from empty numbers:

xsl:template name="teaserImage">
  <xsl:param name="currentPage" />

  <xsl:if test="number($currentPage/data[@alias='teaserImage'])">
    <xsl:copy-of select="umbraco.library:GetMedia($currentPage/data[@alias='teaserImage'], 'false')" />
  </xsl:if>
</xsl:template>

<xsl:variable name="teaserImage_XML">
  <xsl:call-template name="teaserImage">
    <xsl:with-param name="currentPage" select="$currentPage" />
  </xsl:call-template>
</xsl:variable>

<xsl:variable name="teaserImage" select="msxml:node-set($teaserImage_XML)" />

But I can not use template result directly in xpath. To conver result into node set, I store XML into template variable teaserImage_XML and then store converted node-set into variable teaserImage.

Is there exist better way to return node-set from template? Without using template variable.