xsl:sort with nulls at end

Saxon parser
Xslt 2

I am sorting XML using xsl:sort. It looks something like this.

<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="2.0">
   <xsl:template match="REPORT">
      <xsl:copy>
         <xsl:for-each select="*">
            <xsl:sort select="X" order="ascending" data-type="text"/>
            <xsl:sort select="Y" order="descending" data-type="text"/>
            <xsl:sort select="Z" order="ascending" data-type="number"/>
            <xsl:copy-of select="."/>
         </xsl:for-each>
      </xsl:copy>
   </xsl:template>
   <xsl:template match="*">
      <xsl:copy>
         <xsl:apply-templates/>
      </xsl:copy>
   </xsl:template>
</xsl:transform>

The issue I have is that if the row is missing that tag, the sort puts
that record first. Ie. Nulls come first. I need the nulls to come last.
Is there a way to get around this and force the nulls to be last?

Thanks,
Rebecca


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