How to reproduce:
1. Create a new project in your preferred workspace and open it
2. Connect it to Perforce
3. Create a new material and try to submit it (Keep the Submit Window open)
4. While the Submit Window is open, create a new C# script in the Project Window
5. Observe the asset list in the Submit Window

Expected result: the asset list is still saved in the Submit Window when the VCS Window is refreshed from the script's creation
Actual result: the asset list is cleared and you can no longer submit whatever you were trying to submit

Reproduced in: 2020.1.0a18, 2019.3.0f4, 2019.2.16f1, 2018.4.15f1, 2017.4.36f1