Fix hangup button handler

src/vector/jitsi/index.ts

@@ -116,8 +116,9 @@ let meetApi: any; // JitsiMeetExternalAPI
 
             // TODO: register widgetApi listeners for PTT controls (https://github.com/vector-im/riot-web/issues/12795)
 
-            widgetApi.on('hangup', () => {
+            widgetApi.addEventListener('hangup', (ev: CustomEvent<IWidgetApiRequest>) => {
                 if (meetApi) meetApi.executeCommand('hangup');
+                widgetApi.transport.reply(ev.detail, {}); // ack
             });
         } else {
             enableJoinButton();