Update to Unity2017, builtin resource did't hava "Sprites-Default.mat"

Questions & Answers
1

I updated my project’s unity version from unity5.3 to unity2017, there were some error appeared.
One of the errors was “Assertion failed: Failed to find Sprites-Default.mat”, it caused by “Resources.GetBuiltinResource( “Sprites-Default.mat”)”.
“Resources.GetBuiltinResource” is a undocument function, but unity5.3 was used well.
How can i fix this error or replace this use？

2

In Unity2017, need to change code below:

#if UNITY_EDITOR
    Material mat_sprite_default = UnityEditor.AssetDatabase.GetBuiltinExtraResource<Material>("Sprites-Default.mat");
#else
    Material renderer.material = Resources.GetBuiltinResource<Material>("Sprites-Default.mat");
#endif