Empty records are rendered incorrectly in bridgedoc

[io7m]

An empty record yields documentation like this:

<h4>Fields</h4>
 <table class="cbFieldsTable">
    <thead>
       <tr>
          <th>Name</th>
          <th>Type</th>
          <th>Description</th>
       </tr>
    </thead>
    <tbody/>
 </table>

It should yield a simple paragraph that says "there are no fields" the same way variant cases are rendered.