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<xsl:stylesheet
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<xsl:param name="currentPage"/>

<xsl:template match="/">

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  <xsl:variable name="testNode" select="umbraco.library:GetXmlNodeById(1000)" />

  <!-- this line errors, comment out this line to see the rest work -->
  <xsl:value-of select="umbraco.library:NiceUrl($testNode/@id)" />

  <!-- this line works because of the if block -->
  <xsl:if test="$testNode/@id != ''">
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