Reproduction steps:
1. Open attached project "Emit_Bug"
2. Play the Particle System on GameObject in New Scene (In Editor mode)
3. Restart the Particle System
Expected result: EmitParams Properties get overwritten only when given a value as stated in Documentation
Actual result: EmitParams Properties get overwritten with empty values when no values are assigned
Reproducible with: 2018.4.28f1, 2019.4.13f1, 2020.1.10f1, 2020.2.0b8, 2021.1.0a1