The markup below produces an empty line in a <step> as in
http://i.imgur.com/IuI75d3.png
<step xml:id="test_middleware_step">
<para>Test the middleware from outside of DevStack on
a remote machine that has access to your DevStack
instance.</para>
<substeps>
<step>
<screen><userinput>swift --os-auth-url=http://203.0.113.68:5000/v2.0/ --os-region-name=RegionOne --os-username=demo:demo --os-password=devstack list middleware-test</userinput></screen>
</step>
<step>
<screen>Container GET failed: http://203.0.113.68:8080/v1/AUTH_.../middleware-test?format=json 403 Forbidden You shall not pass!</screen>
</step>
</substeps>
</step>
It seems that the xml:id is the culprit as I can reproduce the error in other <step> tags by adding an xml:id.
we usually click the "bug report" button on the right top of the specific page, then the bug description can have details of that page, so we can confirm it easily
anyway, thanks for reporting this