Ultimate SkyWars 1.5.7

The set spawn command don’t work . It gave me the stick caller wand but when I select the spawn it shows error in console (2021-01-22 12:26:15.784 [main] FATAL - Exception while invoking run
java.lang.NullPointerException: Cannot invoke "cn.nukkit.inventory.PlayerInventory.setItem(int, cn.nukkit.item.Item)" because the return value of "cn.nukkit.Player.getInventory()" is null)

At the last update it doesn't work, wrong plugin manager fix it for more star's