In Unity 2018.2, when attempting to use the "AssetDatabase.LoadAllAssetsAtPath" to load the assets from either "Library/unity default resources" or "Resources/unity_builtin_extra", a Object[] is returned populated with the corresponding assets stored within. However, if you attempt to do this in Unity 2018.3, the returned Object[] is empty.

To reproduce:

1. Download attached project "2018.2 - LoadDefaultandBuiltinResources.zip and open in Unity
2. Press the Menu item labelled "Tests" and execute both functions "Library > unity default resources" and "Resources > unity_builtin_extra"
3. Observe that the text printed to the Console states that no objects were loaded

Expected behavior: Using LoadAllAssetsAtPath to load the paths would load the objects stored at the path
Actual behavior: Using LoadAllAssetsAtPath to load the paths does not load objects stored at paths, and leaves the expecting Object[] empty

Notes:
- This issue appears on both Windows and macOS

Reproduced on Unity 2018.3.0a1, 2018.3.0f1 and 2019.1.0a11
Not reproduced on Unity 2018.2.19f1
Regression on Unity 2018.3.0a1