Instantiate GameObject in unity

This part of script works in editor, but in WindowsPlayer get Object reference error, can anybody help?

WWW download= new WWW ("URL"); yield return download;

AssetBundleCreateRequest assetBundleCreateRequest = AssetBundle.CreateFromMemory(download.bytes); yield return assetBundleCreateRequest;

AssetBundle assetBundle = assetBundleCreateRequest.assetBundle; yield return assetBundle;

try { 	GameObject go = Instantiate(assetBundle.Load("objectName",typeof(GameObject))) as GameObject; } catch(Exception e) { 	ErrorLoger.Log(e.ToString()); }

Problem is in AssetBundle assetBundle = assetBundleCreateRequest.assetBundle; yield return assetBundle;, can not get asset bundle