For gtn/news frames, ensure frame is engaged prior to dismissal.

Guarding here is simpler than tracking event handlers and making
assumptions.

config/plugins/webhooks/gtn/script.js

@@ -3,7 +3,10 @@
     var lastUpdate = 0;
 
     function removeOverlay() {
-        document.getElementById("gtn-container").style.visibility = "hidden";
+        const container = document.getElementById("gtn-container");
+        if (container) {
+            container.style.visibility = "hidden";
+        }
     }
 
     function showOverlay() {

config/plugins/webhooks/news/script.js

@@ -1,6 +1,9 @@
 (function () {
     function hideNewsOverlay() {
-        document.getElementById("news-container").style.visibility = "hidden";
+        const container = document.getElementById("news-container");
+        if (container) {
+            container.style.visibility = "hidden";
+        }
     }
 
     function newsSeen() {