Build failure for footnotes

[lcawl]

Footnotes should work in our documentation as described in https://asciidoctor.org/docs/user-manual/#user-footnotes

The following works fine:

Internode-communication over the transport protocol in the {es} cluster.footnote:[<<tls-transport>>]

However when I try to use footnotes in a list, the build fails. For example:

* Internode-communication over the transport protocol in the {es} cluster.footnote:[<<tls-transport>>]

... results in an error like this when I build the Elasticsearch Reference:

INFO:build_docs:---err---
INFO:build_docs:/docs_build/resources/asciidoctor/lib/docbook_compat/convert_lists.rb:51:in `block in munge_list_items': Couldn't remove <p> for Internode-communication over the transport protocol in the Elasticsearch cluster.<sup class="footnote">[<a id="_footnoteref_5" class="footnote" href="#_footnotedef_5" title="View footnote.">5</a>]</sup> in <div class="ulist itemizedlist"> (RuntimeError)
INFO:build_docs:<ul class="itemizedlist">
INFO:build_docs:<li class="listitem">
INFO:build_docs:<p>Internode-communication over the transport protocol in the Elasticsearch cluster.<sup class="footnote">[<a id="_footnoteref_1" class="footnote" href="#_footnotedef_1" title="View footnote.">1</a>]</sup></p>
INFO:build_docs:</li>

[gtback]

This seems like an error in our docbook compat extension for asciidoctor. The error message is pretty clear and points straight to where the error is coming from. This might be a good one for me to take a look at to get familiar with our Ruby code.