https://github.com/ruby/ruby/commit/e4e054e3ce40 used four footnotes without blank lines. And the ChangeLog generated from that commit resulted in ``undefined method `parts' for nil`` error. For now, let a footnote terminated by the next footnote mark. Also refined the error message when undefined footnote is used. https://github.com/ruby/rdoc/commit/a7f290130b
RubyVM
you don't have to