User gets "Assets/ .scenetemplate' is not a valid asset file name" error during scene template saving

To reproduce:

1. Open HUB;
2. Create a new project;
3. Go to menu "File" and select "Save as Scene Template...";
4. In "Save scene" popup remove "SampleScene" text from "Save As" field;
5. Verify, that "Save" button becomes disabled. Good.
6. Go back to the same field and add space;
7. Verify, that "Save" button becomes active again;
8. Click "Save".

 
Expected Result:  "Sample Scene (Scene Template Asset)" should be created.
Actual Result: Console window displays errors.

Reproducible with: 2023.1.0a11, 2022.2.0a3.
Not Reproducible with: 2022.1.16f1, 2021.3.10f1, 2020.3.40f1.