[LayaAir 2.0]Unity 导出Terrain报错

在Unity场景中仅仅添加一个Terrain，导出场景报错
 
 TypeLoadException: Could not load type 'UnityEngine.TerrainLayer' from assembly 'UnityEngine, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
p.g (UnityEngine.GameObject A_0, .g A_1)
p.a (UnityEngine.GameObject A_0, .g A_1, .g A_2, Vector3 A_3, Quaternion A_4, Vector3 A_5, System.String& A_6)
p.a (UnityEngine.GameObject A_0, System.String A_1, .g A_2, Boolean A_3, Boolean A_4, Boolean A_5)
p.j ()
p.k ()
p.b (System.String A_0)
LayaAir3D.exportResource (Boolean isDebug, Int32 Platformindex, System.String lastname)
a+k.b ()
m.b (.a A_0)
m.a ()
UnityEditor.EditorApplication.Internal_CallUpdateFunctions () (at C:/buildslave/unity/build/Editor/Mono/EditorApplication.cs:191)