fixed arena transfer with empty inventory slots and blocked advancements in the arena

craftattack/src/main/java/eu/mhsl/craftattack/spawn/craftattack/appliances/metaGameplay/arenaPortal/ArenaPortal.java

@@ -20,7 +20,6 @@ import org.bukkit.event.Listener;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
 
-import java.util.ArrayList;
 import java.util.Base64;
 import java.util.HashSet;
 import java.util.List;
@@ -75,8 +74,7 @@ public class ArenaPortal extends Appliance {
         if(!this.pendingTransfers.add(player.getUniqueId())) return;
         player.sendActionBar(Component.text("Du wirst zur Arena gebracht...", NamedTextColor.GRAY));
 
-        List<ItemStack> contents = new ArrayList<>(List.of(player.getInventory().getContents()));
-        String items = Base64.getEncoder().encodeToString(ItemStack.serializeItemsAsBytes(contents));
+        String items = Base64.getEncoder().encodeToString(ItemStack.serializeItemsAsBytes(player.getInventory().getContents()));
         ArenaRepository.InventorySnapshot snapshot = new ArenaRepository.InventorySnapshot(player.getUniqueId(), items);
 
         Bukkit.getScheduler().runTaskAsynchronously(Main.instance(), () -> {