Duplicate Player Tag save fails silently with no error or validation message

Steps to reproduce:

1. Create a project
2. Go to Window -> Multiplayer -> Multiplayer Center
3. Select any “Genre of your Game” and “Number of Players per Session” dropdown options in the Multiplayer Center window
4. Click the "Install Packages" button
5. Go to "Edit > Project Settings…"
6. Press “+” and enter "123" and click "Save"
7. Click "+" and enter "123" one more time and click "Save"
8. Observe the result

Actual results: Nothing happens

Expected results: The users should get a validation message that the entered tag already exists, and they have to update it or enter another one

Reproducible with versions: 6000.0.67f1, 6000.3.8f1, 6000.4.0b8, 6000.5.0a7

Not reproducible with versions: 

Tested on (OS): macOS - Tahoe 26.2