Fix Material.Parse

Should call StandardMaterial.Parse() while the parsedMaterial.customType is "BABYLON.StandardMaterial".

src/Materials/babylon.material.ts

@@ -1307,7 +1307,7 @@
          * @returns - Parsed material.
          */
         public static Parse(parsedMaterial: any, scene: Scene, rootUrl: string): any {
-            if (!parsedMaterial.customType) {
+            if (!parsedMaterial.customType || parsedMaterial.customType === "BABYLON.StandardMaterial" ) {
                 return StandardMaterial.Parse(parsedMaterial, scene, rootUrl);
             }
 
@@ -1323,4 +1323,4 @@
             return materialType.Parse(parsedMaterial, scene, rootUrl);;
         }
     }
-} 
+}