fix: restore Music Blocks loading regression after RequireJS changes (sugarlabs#5632)

- Add robust load guard in index.html for createjs
- Enhance activity.js initialize() to wait for critical globals (Tone, libgif, etc.)
- Make Activity constructor defensive against missing GIFAnimator
- Fix potential ReferenceError in index.html doSearch() call

Co-authored-by: Walter Bender <walter@sugarlabs.org>

Author: vanshika2720

index.html

@@ -548,6 +548,13 @@
     <script>
         let canvas, stage;
         function init() {
+            // Defensive check: ensure createjs is loaded before using it
+            if (typeof createjs === "undefined") {
+                // Retry after a short delay if createjs isn't ready yet
+                setTimeout(init, 50);
+                return;
+            }
+
             canvas = document.getElementById("canvas");
             stage = new createjs.Stage(canvas);
 
@@ -608,7 +615,12 @@
     </script>
     <script>
         $(document).ready(function () {
-            doSearch();
+            // Defensive check for doSearch global (now an Activity member)
+            if (typeof doSearch === "function") {
+                doSearch();
+            } else if (window.activity && typeof window.activity.doSearch === "function") {
+                window.activity.doSearch();
+            }
         });
     </script>
 

js/activity.js

@@ -306,9 +306,12 @@ class Activity {
         this.loadAnimationIntervalId = null;
 
         // Initialize GIF animator
-        // Check if GIFAnimator is available before using it
         if (typeof GIFAnimator !== "undefined") {
             this.gifAnimator = new GIFAnimator();
+        } else {
+            // eslint-disable-next-line no-console
+            console.debug("GIFAnimator not yet available in constructor");
+            this.gifAnimator = null;
         }
 
         // Dirty flag for canvas rendering optimization
@@ -485,6 +488,11 @@ class Activity {
             this.helpfulWheelItems = [];
 
             this.setHelpfulSearchDiv();
+
+            // Late initialization of GIF animator if it was missed in constructor
+            if (!this.gifAnimator && typeof GIFAnimator !== "undefined") {
+                this.gifAnimator = new GIFAnimator();
+            }
         };
 
         /*
@@ -7786,7 +7794,15 @@ const activity = new Activity();
 // Execute initialization once all RequireJS modules are loaded AND DOM is ready
 define(["domReady!"].concat(MYDEFINES), doc => {
     const initialize = () => {
-        if (typeof createDefaultStack !== "undefined") {
+        // Defensive check for multiple critical globals that may be delayed
+        // due to 'defer' execution timing variances.
+        const globalsReady = typeof createDefaultStack !== "undefined" &&
+                           typeof createjs !== "undefined" &&
+                           typeof Tone !== "undefined" &&
+                           typeof GIFAnimator !== "undefined" &&
+                           typeof SuperGif !== "undefined";
+
+        if (globalsReady) {
             activity.setupDependencies();
             activity.domReady(doc);
             activity.doContextMenus();
@@ -7810,7 +7826,7 @@ define(["domReady!"].concat(MYDEFINES), doc => {
                     }
                 );
             } else {
-                setTimeout(initialize, 10);
+                setTimeout(initialize, 50); // Increased delay slightly
             }
         }
     };