Setting the Material.shaderKeywords field causes the field to become empty when the new shader keywords are the same as the existing ones

How to reproduce:

1. Open the attached project "TestShaderKeywordBug2020-main.zip"
2. Open Assets/Scenes/SampleScene.unity
3. Enter Play Mode
4. Click the "Button" Button in the Game view window

Expected results: The text stays the same in the Game view window
Actual results: The text changes to "Keywords:"

Reproducible with: 2021.2.18f1, 2021.3.18f1, 2022.2.7f1, 2023.1.0b4, 2023.2.0a3
Not reproducible with: 2020.3.45f1, 2021.2.17f1

Reproducible on: Windows 10