Update viewer.js

viewer.js

@@ -151,6 +151,7 @@ export async function initializeViewer(config, instanceId) {
     app.root.addChild(modelEntity);
 
     // --- Add the GLB entity ---
+    let matTransparent = null;
     if (assets.glb && assets.glb.resource && assets.glb.resource.instantiateRenderEntity) {
       const glbEntity = assets.glb.resource.instantiateRenderEntity();
       app.root.addChild(glbEntity);