Saxon-EE 9.8.0.14J from Saxonica
Java version 10.0.2 and Java version 11

java.lang.IllegalArgumentException: Attempting to treat a parent pointer as a node
	at net.sf.saxon.tree.tiny.TinyTree.getNode(TinyTree.java:939)
	at net.sf.saxon.tree.tiny.SiblingIterator.next(SiblingIterator.java:128)
	at net.sf.saxon.tree.tiny.SiblingIterator.next(SiblingIterator.java:31)
	at net.sf.saxon.value.SequenceExtent.<init>(SequenceExtent.java:86)
	at net.sf.saxon.value.SequenceExtent.makeResidue(SequenceExtent.java:134)
	at net.sf.saxon.om.FocusTrackingIterator.getLength(FocusTrackingIterator.java:146)
	at net.sf.saxon.expr.XPathContextMinor.getLast(XPathContextMinor.java:204)
	at com.saxonica.config.EnterpriseConfiguration$4.getLength(EnterpriseConfiguration.java:1953)
	at net.sf.saxon.tree.iter.ManualIterator.getLength(ManualIterator.java:123)
	at net.sf.saxon.expr.XPathContextMinor.getLast(XPathContextMinor.java:204)
	at net.sf.saxon.functions.PositionAndLast$Last.evaluateItem(PositionAndLast.java:152)
	at net.sf.saxon.functions.PositionAndLast.call(PositionAndLast.java:128)
	at net.sf.saxon.functions.PositionAndLast$Last.call(PositionAndLast.java:150)
	at net.sf.saxon.expr.FunctionCall.iterate(FunctionCall.java:547)
	at net.sf.saxon.expr.Expression.evaluateItem(Expression.java:849)
	at net.sf.saxon.expr.ValueComparison.effectiveBooleanValue(ValueComparison.java:691)
	at net.sf.saxon.expr.instruct.Choose.choose(Choose.java:901)
	at net.sf.saxon.expr.instruct.Choose.processLeavingTail(Choose.java:876)
	at net.sf.saxon.expr.instruct.Block.processLeavingTail(Block.java:687)
	at net.sf.saxon.expr.LetExpression.processLeavingTail(LetExpression.java:709)
	at net.sf.saxon.expr.instruct.Block.processLeavingTail(Block.java:687)

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Saxon-EE 9.9.0.1J from Saxonica
Java version 10.0.2 and Java version 11

java.lang.IllegalArgumentException: Attempting to treat a parent pointer as a node
	at net.sf.saxon.tree.tiny.TinyTree.getNode(TinyTree.java:956)
	at net.sf.saxon.tree.tiny.NamedChildIterator.next(NamedChildIterator.java:79)
	at net.sf.saxon.tree.tiny.NamedChildIterator.next(NamedChildIterator.java:23)
	at net.sf.saxon.om.SequenceIterator.forEachOrFail(SequenceIterator.java:127)
	at net.sf.saxon.value.SequenceExtent.<init>(SequenceExtent.java:83)
	at net.sf.saxon.value.SequenceExtent.makeResidue(SequenceExtent.java:146)
	at net.sf.saxon.om.FocusTrackingIterator.getLength(FocusTrackingIterator.java:129)
	at net.sf.saxon.expr.XPathContextMinor.getLast(XPathContextMinor.java:217)
	at com.saxonica.config.EnterpriseConfiguration$2.getLength(EnterpriseConfiguration.java:2056)
	at net.sf.saxon.tree.iter.ManualIterator.getLength(ManualIterator.java:116)
	at net.sf.saxon.expr.XPathContextMinor.getLast(XPathContextMinor.java:217)
	at net.sf.saxon.functions.PositionAndLast$Last.evaluateItem(PositionAndLast.java:150)
	at net.sf.saxon.functions.PositionAndLast.call(PositionAndLast.java:126)
	at net.sf.saxon.functions.PositionAndLast$Last.call(PositionAndLast.java:148)
	at net.sf.saxon.expr.FunctionCall.iterate(FunctionCall.java:532)
	at net.sf.saxon.expr.Expression.evaluateItem(Expression.java:846)
	at net.sf.saxon.expr.ValueComparison.effectiveBooleanValue(ValueComparison.java:697)