message: Fix event call
diff: @@ -208,7 +208,7 @@ export default class WidgetMessaging extends MatrixPostMessageApi {
  startListening() {
  this.start();
  if (global.mxWidgetMessagingListenerCount === 0) {
  - window.addEventListener("message", () => this.onMessage, false);
  + window.addEventListener("message", (evt) => this.onMessage(evt), false);
  }
  global.mxWidgetMessagingListenerCount += 1;
  }
  