Steps to reproduce:

1. Download attached project and open in Unity.
2. In the Project, select the ParticleOld material.
3. Check the Inspector and observe that the Emission checkbox is disabled.
4. Install the Universal Render Pipeline via the Package Manager.
5. Open RP Converter >> Window >> Rendering >> Render Pipeline Converter.
6. Select the Material Upgrader.
7. Press on Initialize and Convert.
8. Select ParticleOld material in the Inspector.

Observe: The Emission channel checkbox will be enabled.

Actual results: The Emission checkbox is enabled, but it should stay disabled after the conversion.

Expected results: The Emission checkbox should not be enabled, because it was disabled before the conversion.

Reproducible with versions: 

6000.2.12f1. 6000.5.0a3

Note:

Not reproducible when converting Standard materials