Repro steps:
1. Open SampleScene from the attached project
2. Select the Particle System, expand Texture Sheet Animation and observe the warning message
3. Observe in the scene view that only 1 of the sprites shows
4. Enter play mode
5. Observe both sprites show and the warning message is gone

Expected outcomes:
- With the correct setup, no warning message to show and for both sprites to show outside of play mode
- All sprites from the atlas to show both in and outside of play mode

Notes:
- entering play mode once and existing fixes the warning message and the atlas showing both sprites
- hurts discoverability as the atlas doesn't initially work and the warning message is actively mentioning a wrong setup, even when it's correct
- hurts workflow, as any change in the atlas requires entering/exiting play mode to be able to see the changes