Error unlinking empty document in jruby

[wobh]

My coworker and I ran into this funny case where the jruby version of Nokogiri kicks up an error that MRI does not:

~% jruby -e "require 'nokogiri'; Nokogiri::HTML::DocumentFragment.parse('').unlink"
RuntimeError: TYPE: 11 PARENT NULL
  unlink at nokogiri/XmlNode.java:1313
  (root) at -e:1
~% ruby -e "require 'nokogiri'; Nokogiri::HTML::DocumentFragment.parse('').unlink"
~%

The case for this is easily avoided with blank checking, but we were wondering if there was any explanation for it. Thanks!