fix(Demo): Interact with queueManager before do any adManager operation (#8894)

Related to
#8529 (comment)

Author: avelad

demo/main.js

@@ -1384,6 +1384,9 @@ shakaDemo.Main = class {
         ui.configure(uiConfig);
       }
 
+      const queueManager = this.player_.getQueueManager();
+      await queueManager.removeAllItems();
+
       if (asset.hasAds()) {
         // The player internally, if another stream is loaded, calls
         // adManager.onAssetUnload and this would prevent the initial preloading
@@ -1426,9 +1429,6 @@ shakaDemo.Main = class {
         }
       }
 
-      const queueManager = this.player_.getQueueManager();
-      await queueManager.removeAllItems();
-
       // Finally, the asset can be loaded.
       if (asset.preloadManager) {
         const preloadManager = asset.preloadManager;