navigation: error when end is member constructing a node on the self-axis

[lueck]

navigation.xsl throws an error, when the end member constructs a node on the self-axis of the parent member's subtree. – This description may miss the issue's reason.

Example:

target/bin/xslt.sh -config:saxon.he.xml -xsl:xsl/navigation.xsl -s:test/john.xml tree=page-hateoas start=p.1.start end=p.2.start
Error on line 166 column 54 of tree.xsl:
  XTTE0590  The string "" cannot be cast to a boolean
  In template rule with match="element(Q{http://www.tei-c.org/ns/1.0}citeStructure)" on line 166 of tree.xsl
     invoked by built-in template rule (shallow-skip)
     invoked by xsl:apply-templates at file:/home/clueck/src/scdh/tei-processing/dts-transformations/xsl/tree.xsl#93
During lazy evaluation of xsl:apply-templates on line 93 of file:/home/clueck/src/scdh/tei-processing/dts-transformations/xsl/tree.xsl
During lazy evaluation of let $members := ... on line 92 of file:/home/clueck/src/scdh/tei-processing/dts-transformations/xsl/tree.xsl
In function dts:members on line 69 column 81 of tree.xsl:
     invoked by function call at file:/home/clueck/src/scdh/tei-processing/dts-transformations/xsl/navigation.xsl#121
  In template rule with match="/" on line 102 of navigation.xsl
The string "" cannot be cast to a boolean