Try to search for a GUIStyle. This functions returns NULL and does not give an error.
using UnityEngine; using System.Collections;
public class ExampleClass : MonoBehaviour { public string aStyleName = "A Style I have"; void OnGUI() { if (GUI.skin.FindStyle(aStyleName) == null) Debug.LogWarning("No style named \"" + aStyleName + "\" could be found"); } }