nba(jump ball): cadence

* Fix pre{}.

contracts/JumpBall.cdc

@@ -251,13 +251,13 @@ access(all) contract JumpBall {
 
     // Add an opponent to a game
     access(all) fun addOpponent(gameID: UInt64, player: &Player) {
-        let game = JumpBall.games[gameID] ?? panic("Game does not exist.")
-
         pre {
             game.opponent == nil: "Opponent has already been added."
             player.canCreateGame(): "Player does not have a valid collection capability to be added as an opponent."
         }
 
+        let game = JumpBall.games[gameID] ?? panic("Game does not exist.")
+
         game.opponent = player.address
         game.opponentCap = player.collectionCap
         JumpBall.addGameForUser(player.address, gameID)
@@ -297,13 +297,13 @@ access(all) contract JumpBall {
 
     // Destroy a game and clean up resources
     access(all) fun destroyGame(gameID: UInt64) {
-        let game <- JumpBall.games.remove(key: gameID) ?? panic("Game does not exist.")
-
         // Ensure all NFTs have been withdrawn
         pre {
             game.nfts.isEmpty: "All NFTs must be withdrawn before destroying the game."
         }
 
+        let game <- JumpBall.games.remove(key: gameID) ?? panic("Game does not exist.")
+
         // Remove game from userGames mapping
         JumpBall.removeGameForUser(game.creator, gameID)
         if let opponent = game.opponent {