[LayaAir 1.0]LayaAir3D导出scene 报错

LayaAir3d 1.7.16 unity 5.6.1 导出场景的时候报错 报错信息如下：
TypeLoadException: Could not load type 'UnityEngine.ImageConversion' from assembly 'LayaAirLibrary'.
LayaExport.DataManager.getSceneNode ()
LayaExport.DataManager.saveData ()
LayaExport.DataManager.getData ()
LayaAir3D.exportResource (Boolean isDebug) (at Assets/LayaAir3D/LayaTool/LayaAir3D.cs:435)
LayaAir3D.OnGUI () (at Assets/LayaAir3D/LayaTool/LayaAir3D.cs:337)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)