When force-unique==true, preprocess2 does not properly process duplicated topics

[chrispy-snps]

Expected Behavior

With the following testcase:

when an HTML5 transformation using preprocess2 is run with force-unique==true, references to the duplicated topics should be computed correctly.

Actual Behavior

The index.html file contains an invalid link for a duplicate topic:

<nav>
  <ul class="map">
    <li class="topicref"><a href="topic.html">My Topic</a></li>
    <li class="topicref"><a href="2b41d63b9eaac30156c27585f2329ccd518d1f9b.html">My Topic</a></li>
  </ul>
</nav>

In the topic, both key references point to the topic that was published correctly:

<div class="body">
  <p class="p"><a class="xref" href="topic.html">My Topic</a></p>
  <p class="p"><a class="xref" href="topic.html">My Topic</a></p>
</div>

Steps to Reproduce

1. Download the following testcase:
   4429.zip
2. Run the following command:
   dita -i map.ditamap -f html5 -Dforce-unique=true

Environment

• DITA-OT version: 4.2.2-prerelease
• Operating system and version: Linux (Ubuntu 22.04-LTS)
• How did you run DITA-OT? dita command
• Transformation type: HTML5