Handle map reset when the game is loaded/unloaded.

https://github.com/dcs-liberation/dcs_liberation/issues/2039

Partial fix for
https://github.com/dcs-liberation/dcs_liberation/issues/2045 (now works
in the new map, old one not fixed yet).

game/server/navmesh/routes.py

@@ -9,7 +9,9 @@ router: APIRouter = APIRouter(prefix="/navmesh")
 
 
 @router.get("/", response_model=list[NavMeshPolyJs])
-def get(for_player: bool, game: Game = Depends(GameContext.get)) -> list[NavMeshPolyJs]:
+def get(
+    for_player: bool, game: Game = Depends(GameContext.require)
+) -> list[NavMeshPolyJs]:
     mesh = game.coalition_for(for_player).nav_mesh
     return [
         NavMeshPolyJs(