EventSource: ignore IDs with U+0000

Tests: web-platform-tests/wpt#6584.

Fixes whatwg#689.

Author: annevk

source

@@ -94056,8 +94056,9 @@ dictionary <dfn>EventSourceInit</dfn> {
      data-x="concept-event-stream-last-event-id">last event ID string</span> is not the empty
      string, <span data-x="concept-header-list-set">set</span> `<code
      data-x="http-last-event-id">Last-Event-ID</code>`/<span
-     data-x="concept-event-stream-last-event-id">last event ID string</span>, encoded as UTF-8, in
-     <var>request</var>'s <span data-x="concept-request-header-list">header list</span>.</p></li>
+     data-x="concept-event-stream-last-event-id">last event ID string</span>, <span data-x="UTF-8
+     encode">encoded as UTF-8</span>, in <var>request</var>'s <span
+     data-x="concept-request-header-list">header list</span>.</p></li>
 
      <!--FETCH--><li><p><span data-x="concept-fetch">Fetch</span> <var>request</var> and process the
      response obtained in this fashion, if any, as described earlier in this section.</p></li>
@@ -94201,7 +94202,8 @@ any-char      = %x0000-0009 / %x000B-000C / %x000E-10FFFF
 
    <dt>If the field name is "id"</dt>
 
-   <dd><p>Set the <var>last event ID</var> buffer to the field value.</p></dd>
+   <dd><p>If the field value does not contain U+0000 NULL, then set the <var>last event ID</var>
+   buffer to the field value. Otherwise, ignore the field.</p></dd>
 
 
    <dt>If the field name is "retry"</dt>