Steps to reproduce:
1. Open the original project
2. Navigate to Project -> Scenes and open "SampleScene"
3. In Hierarchy window select "Particle system"
4. In the Inspector window scroll down and enable "Texture Sheet Animation"
5. Notice how the Trails of the Particle System change after enabling "Texture Sheet Animation"

Expected results: Particle System Trails renders its materials
Actual results: Particle SystemTrails texture is being overridden by the Texture from the Texture Sheet Animation

Reproducible with: 2018.3.0a6, 2018.1.0b3, 2019.2.0a5
Not Reproducible with: 2017.4.20f2, 2018.2.18f1, 2018.3.0a5