Reproduction Steps:
1. Open attached project.
2. Open "Lobby" scene.
3. Enter Play mode.
4. Create a game.
5. Open attached Standalone Player "network lobby test".
6. Select "List Servers".
7. Join created game.
8. Select "Back".

Expected result: Standalone Player returns to Server list.
Actual result: Standalone Player crashes.

Reproducible on: 5.6.0b6

Note: Not reproducible on previous versions.