How to reproduce:
1. Open given Unity project
2. Enter "SampleScene" scene
3. Select SpriteAtlas item in the menu and then click "TestModify"
4. Notice that image below "Atlas" disappeared
5. Few times repeat step 3 and notice that nothing has changed
6. Create a new sprite in the Project view
7. Notice that image below the Atlas appeared

Expected result: Sprites should be rendered after SpriteAtlasExtensions.SetPlatformSettings() and SpriteAtlasUtility.PackAtlases()
Actual result: Sprite is not rendered

Reproducible with: 2018.3.0a1, 2018.2.0b4
Cannot be tested with versions below 2018.2 because of Assets/Editor/ModifySpriteAtlasSettings.cs(24,13): error CS0122: `UnityEditor.U2D.SpriteAtlasExtensions' is inaccessible due to its protection level errors