Link icon fails to show up for all links on the page when any header ID is exactly 'module'

Problem/Motivation

The external link icon will not show up for any of the external links on the page when any given anchor ID is exactly 'module'.

To reproduce, try the following:

<h2 id="foo">Title 1</h2>

<p>A <a href="https://www.drupal.org/project/extlink">link</a>.</p>

<h2 id="bar">Title 2</h2>

<p>Another <a href="https://www.drupal.org/node/131949/commits">link</a>.</p>

<h2 id="module">Title 3</h2>

<p>One last <a href="https://www.drupal.org/node/2834289">link</a>.</p>

Proposed resolution

TBD.

Remaining tasks

Understand why this particular string is causing the module to fail to display the icon next to all links on the page.

User interface changes

The expected external link icon should now appear on all pages, even those with 'module' as an anchor ID

API changes

None.

Data model changes