fixed null reference error in FileHelper

VECTO3GUI2020/Helper/FileHelper.cs

 using System.IO;
+using Castle.Core.Internal;
 
 namespace VECTO3GUI2020.Helper
 {
@@ -7,7 +8,9 @@ namespace VECTO3GUI2020.Helper
 		public static void CreateDirectory(string fileName)
 		{
 			var dirName = Path.GetDirectoryName(fileName);
-			Directory.CreateDirectory(dirName);
+			if (!dirName.IsNullOrEmpty()) {
+				Directory.CreateDirectory(dirName);
+			}
 		}
 	}
 }
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