Exception when adding Language dynamically

public void AddLanguage( string LanguageName, string LanguageCode )
		{
			if (GetLanguageIndex(LanguageName, false)>=0)
				return;

			LanguageData Lang = new LanguageData();
				Lang.Name = LanguageName;
				Lang.Code = LanguageCode;
			mLanguages.Add (Lang);

			int NewSize = mLanguages.Count;
			for (int i=0, imax=mTerms.Count; i<imax; ++i)
			{
				Array.Resize(ref mTerms[i].Languages, NewSize);
				Array.Resize(ref mTerms[i].Flags, NewSize);
			}
			#if UNITY_EDITOR
//!!!! ownerObject is null, causing an exception. !!!
				UnityEditor.EditorUtility.SetDirty(this.ownerObject);   

			#endif
		}
}