Add defensive check for missing mode and modeText elements (#5263)

Author: Chaitu7032

script.js

@@ -3,7 +3,7 @@
  * @function
  * @global
  */
-$(document).ready(function() {
+$(document).ready(function () {
     /**
      * The user's selected mode, stored in local storage.
      * @type {string}
@@ -29,6 +29,11 @@ $(document).ready(function() {
      */
     var modeText = document.getElementById("modeText");
 
+    // Defensive: avoid crashing if expected DOM nodes are missing.
+    if (!modeIcon || !modeText) {
+        return;
+    }
+
     // Set the mode icon and tooltip based on the user's selected mode.
     if (mode === null || mode === "true") {
         modeIcon.innerHTML = "star_border";
@@ -45,6 +50,6 @@ $(document).ready(function() {
     $(".materialize-iso, .dropdown-trigger").dropdown({
         constrainWidth: false,
         hover: false, // Activate on click
-        belowOrigin: true, // Displays dropdown below the button
+        belowOrigin: true // Displays dropdown below the button
     });
 });