Make table.deleteRow(-1) a no-op when there are no rows

This copies the wording of tbody.deleteRow, with "its parent" instead
of "this element". The previous wording would throw for this case.

Tests: web-platform-tests/wpt#4001

source

@@ -38255,19 +38255,16 @@ interface <dfn>HTMLTableElement</dfn> : <span>HTMLElement</span> {
   steps:</p>
 
   <ol>
+   <li><p>If <var>index</var> is less than &#x2212;1 or greater than or equal to the number of
+   elements in the <code data-x="dom-table-rows">rows</code> collection, then throw an
+   <span>"<code>IndexSizeError</code>"</span> <code>DOMException</code>.</p></li>
 
-   <li><p>If <var>index</var> is equal to &#x2212;1, then <var>index</var> must be
-   set to the number of items in the <code data-x="dom-table-rows">rows</code> collection, minus
-   one.</p></li>
-
-   <li><p>Now, if <var>index</var> is less than zero, or greater than or equal to the
-   number of elements in the <code data-x="dom-table-rows">rows</code> collection, the method must
-   instead throw an <span>"<code>IndexSizeError</code>"</span> <code>DOMException</code>, and these
-   steps must be aborted.</p></li>
-
-   <li><p>Otherwise, the method must remove the <var>index</var>th element in the <code
-   data-x="dom-table-rows">rows</code> collection from its parent.</p>
+   <li><p>If <var>index</var> is &#x2212;1, then <span data-x="concept-node-remove">remove</span>
+   the last element in the <code data-x="dom-table-rows">rows</code> collection from its parent, or
+   do nothing if the <code data-x="dom-table-rows">rows</code> collection is empty.</p></li>
 
+   <li><p>Otherwise, <span data-x="concept-node-remove">remove</span> the <var>index</var>th element
+   in the <code data-x="dom-table-rows">rows</code> collection from its parent.</p></li>
   </ol>
 
   </div>