Clarify HTMLHyperlinkElementUtils set the url for absent attribute cases

In the event that the href content attribute is missing, it will be set
to null and it will no longer try to parse the missing attribute.

Fixes #1340.

source

@@ -21494,12 +21494,18 @@ interface <dfn>HTMLHyperlinkElementUtils</dfn> {
   data-x="concept-hyperlink-url">url</dfn> (null or a <span>URL</span>). It is initially null.
 
   <p>An element implementing the <code>HTMLHyperlinkElementUtils</code> mixin has an associated <dfn
-  data-noexport="" data-x="concept-hyperlink-url-set">set the url</dfn> algorithm, which sets this
-  element's <span data-x="concept-hyperlink-url">url</span> to the <span>resulting URL record</span>
-  of <span data-x="parse a url">parsing</span> this element's <code
-  data-x="attr-hyperlink-href">href</code> content attribute value relative to this element's
-  <span>node document</span>. If <span data-x="parse a url">parsing</span> was aborted with an
-  error, set this element's <span data-x="concept-hyperlink-url">url</span> to null.</p>
+  data-noexport="" data-x="concept-hyperlink-url-set">set the url</dfn> algorithm, which runs these
+  steps:</p>
+
+  <ol>
+    <li><p>If this element's <code data-x="attr-hyperlink-href">href</code> content attribute is
+    absent, set this element's <span data-x="concept-hyperlink-url">url</span> to null.</p></li>
+    <li><p>Otherwise, parse this element's <code data-x="attr-hyperlink-href">href</code> content
+    attribute value relative to this element's <span>node document</span>. If <span data-x="parse a
+    url">parsing</span> is successful, set this element's <span
+    data-x="concept-hyperlink-url">url</span> to the result; otherwise, set this element's
+    <span data-x="concept-hyperlink-url">url</span> to null.</li>
+  </ol>
 
   <p>When elements implementing the <code>HTMLHyperlinkElementUtils</code> mixin are created, and
   whenever those elements have their <code data-x="attr-hyperlink-href">href</code> content
@@ -119918,6 +119924,7 @@ INSERT INTERFACES HERE
   Weston Ruter,
   Wilhelm Joys Andersen,
   Will Levine,
+  Will Ray,
   William Chen,
   William Swanson,
   Wladimir Palant,