Retain template conditionals verbatim if param unknown

This is important for template-generating templates.

* src/current/include/preproc/template.xsl (lv:if,lv:unlesS):
  Retain conditional nodes verbatim when referenced param is unknown.

src/current/include/preproc/template.xsl

@@ -749,11 +749,7 @@
           ]/lv:param/@name
         )
       ">
-      <xsl:copy>
-        <xsl:sequence select="@*" />
-
-        <xsl:apply-templates select="*" mode="preproc:apply-template" />
-      </xsl:copy>
+      <xsl:sequence select="." />
     </xsl:when>
 
     <xsl:otherwise>