fix TypeError on obsolete_browser_alert innerHTML access

Add null check before accessing innerHTML, since the element may not
exist in the DOM when the CMS renders the page.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

groups/home/bootstrap5/home1.js

@@ -36,7 +36,8 @@
 // Display warning if ES6 detection failed
 window.onload = function () {
   if (window.isES6 == false) {
-    document.getElementById("obsolete_browser_alert").innerHTML =
+    var alertEl = document.getElementById("obsolete_browser_alert");
+    if (alertEl) alertEl.innerHTML =
       '<div class="alert alert-danger" role="alert" style="text-align: center;"><strong>WARNING! Unsupported browser!</strong><br />It looks like you\'re using an old browser.<br />This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge.<br />If you continue with this browser, many parts of this site will not work and you will see unexpected results.</div>';
   }
 };