Steps to reproduce:

1. Open attached project
2. Open "dds_test" scene
3. Enter play mode
4. Observe the exception thrown in the console

Expected behavior: Texture2D.LoadRawTextureData() successfully loads texture with mipmaps data
Actual behavior: Texture2D.LoadRawTextureData() fails to load texture with mipmaps data and throws a UnityException

Reproducible with: 5.6.3p3, 2017.1.1p2, 2017.2.0f1, 2017.3.0a7

UnityException: LoadRawTextureData: not enough data provided (will result in overread).
UnityEngine.Texture2D.LoadRawTextureData (System.Byte[] data) (at C:/buildslave/unity/build/artifacts/generated/common/runtime/TextureBindings.gen.cs:322)
dds_script.Copy (UnityEngine.Texture2D cmpTex) (at Assets/dds_script.cs:11)
dds_script.Start () (at Assets/dds_script.cs:34)