allow no selectedoption

source

@@ -53000,8 +53000,8 @@ You cannot submit this form when the field is incorrect.</samp></pre>
    <dd><span>Phrasing content</span>, but there must be no <span>interactive content</span>
    descendant and no descendant with the <code data-x="attr-tabindex">tabindex</code> attribute
    specified.</dd>
-   <dd>If the element is the first child of a <code>select</code> element, then it must have one
-   <code>selectedoption</code> element.</dd>
+   <dd>If the element is the first child of a <code>select</code> element, then it may have zero or
+   one <code>selectedoption</code> element.</dd>
    <dt><span data-x="concept-element-attributes">Content attributes</span>:</dt>
    <dd><span>Global attributes</span></dd>
    <dd><code data-x="attr-fe-disabled">disabled</code></dd>
@@ -55913,9 +55913,9 @@ interface <dfn interface>HTMLSelectedOptionElement</dfn> : <span>HTMLElement</sp
 
   <p>The <code>selectedoption</code> element reflects the contents of a <code>select</code>
   element's currently selected <code>option</code> element. <code>selectedoption</code> elements can
-  be used to declaratively show the selected <code>option</code> element's contents in a different
-  part of the document, such as the <code>select</code> element's invoker button, with alternate
-  rendering based on different selectors in the author's stylesheet.</p>
+  be used to declaratively show the selected <code>option</code> element's contents within the
+  <code>select</code>'s <code>button</code>, with alternate rendering based on different selectors
+  in the author's stylesheet.</p>
 
   <p>Every time the selected <code>option</code> of a <code>select</code> switches from one option
   to another, or the currently selected <code>option</code>'s descendant DOM structure mutates, the