How to reproduce:
1. Create a new project
2. In the Project window Right-click -> Create -> Sprite Atlas
3. Click the newly created Sprite Atlas and In the Inspector window change the "Max Texture Size" and the "Compression" settings
4. Click anywhere in the Hierarchy window to deselect the Sprite Atlas
5. Click on the Sprite Atlas and observe the Inspector

Expected result: Changes to the settings are properly saved
Actual result: Changes to the "Max Texture Size" and "Compression" settings are reset to their default values

Reproduced in: 2018.2.0b4, 2018.2.0a9
Not reproducible in: 2018.2.0a8, 2018.2.0a1, 2018.1.1f1, 2017.4.3f1, 2017.2.3f1, 2017.1.3p4