How to reproduce:
1. Open the attached project ("Repro project")
2. In the Project WIndow select the "case_1104094-Warden_Small" texture and change Its "Max Size" to 1024
3. Open the Sprite Editor and draw two big rectangles onto the sprites
4. Click "Trim" and try to save the changes
5. Observe the Console Window

Expected result: The changes are saved correctly without any errors
Actual result: IndexOutOfRangeException error is thrown

Reproduced in: 2019.1.0a11, 2018.3.0f1, 2018.2.19f1, 2018.2.0b7,
Not reproducible in: 2018.2.0b6, 2018.1.9f2, 2017.4.17f1