[HTML] Fix ToggleEvent source IDL whatwg/html@167802e

Author: triple-underscore

HTML-interaction-ja.html

@@ -118,8 +118,8 @@
 
 ●●options
 
-spec_date:2025-06-02
-trans_update:2025-06-03
+spec_date:2025-06-07
+trans_update:2025-06-08
 source_checked:240603
 page_state_key:HTML
 spec_status:LS
@@ -3612,7 +3612,7 @@ <h4 title="The ToggleEvent interface">6.5.1. `ToggleEvent^I ~interface</h4>
   constructor(DOMString type, optional `ToggleEventInit$I %eventInitDict = {});
   readonly attribute DOMString `oldState$m;
   readonly attribute DOMString `newState$m;
-  readonly attribute `Element$I `source$m1;
+  readonly attribute `Element$I? `source$m1;
 };
 
 dictionary `ToggleEventInit@I : `EventInit$I {