Fix arena leaderboard avatars duplicating or not loading

### Build version
Not specified

### Issue Description
After an arena game ends, the avatars displayed in the leaderboard are either duplicated or fail to load entirely (shown as a white square). This appears to be a long-standing issue present since the arena feature was first introduced.

### STR (Steps to Reproduce)
1. Play an arena game
2. Observe the leaderboard after the game ends

### Expected Result
Avatars in the leaderboard should display correctly and match each player's avatar without duplication.

### Actual Result with evidence
- Avatars in the leaderboard are duplicated, OR
- Avatars fail to load and appear as a white square

(Screenshots attached in the original bug report.)

### Reproduction
Always (100% reproduction index)

### Operative system and additional Notes
Windows

### Related Issues
- #7261 — [QA] Game Arena | Avatar on leaderboard do not match the user's

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Reported by AdventureLand
Requested by Dawid Krajewski (<@U079GRD9WTZ>)

Start by reproducing an arena game on Windows and tracing the leaderboard avatar display after the game ends. Investigate the arena leaderboard and avatar-loading path to compare each displayed avatar with its player; done means all avatars load and match players without duplication.

Written by the indexing model from the issue text.