Cardback turns default if updated while in a game

[Quezler]

Describe the bug

When you update your cardback while you are in a game it will render both in the game and on the list page as your default cardback, caused by this piece of code, likely in place to keep cardbacks private if someone manages to update them in a private game, but this also affects cardbacks in public games.

• [X] Gameplay
• [X] User Interface
• [X] Game Modes
• [ ] Mod Tools
• [ ] Replays
• [ ] Something Else: Please describe

To Reproduce

• change your cardback while in a game and notice it going default

Additional context

• could not find the original reason for that piece of code via git blame, got moved around in the past it seems