修复打包的一个报错

Unity/Assets/Scripts/Core/Helper/FileHelper.cs

@@ -23,6 +23,10 @@ namespace ET
 		
 		public static void CleanDirectory(string dir)
 		{
+			if (!Directory.Exists(dir))
+			{
+				return;
+			}
 			foreach (string subdir in Directory.GetDirectories(dir))
 			{
 				Directory.Delete(subdir, true);		

Unity/Assets/Scripts/Editor/BuildEditor/BuildHelper.cs

@@ -39,12 +39,8 @@ namespace ET
             if (clearFolder && Directory.Exists(fold))
             {
                 Directory.Delete(fold, true);
-                Directory.CreateDirectory(fold);
-            }
-            else
-            {
-                Directory.CreateDirectory(fold);
             }
+            Directory.CreateDirectory(fold);
 
             UnityEngine.Debug.Log("开始资源打包");
             BuildPipeline.BuildAssetBundles(fold, buildAssetBundleOptions, buildTarget);