Solved Getting errors but everything works fine

Made a plugin that prevents player to get in anvil if they have mob_spawner or are receiving it.

Code:

@EventHandler
    public void onInventoryOpenEvent(InventoryOpenEvent e)
    {
        Player player = (Player) e.getPlayer();
        if(e.getInventory().getType() == InventoryType.ANVIL)
        {
            for (ItemStack item : player.getInventory().getContents())
            {
                if(item.getType() == Material.MOB_SPAWNER)
                {
                    e.setCancelled(true);
                    break;
                }               
            }
        }
    }
   
    @EventHandler
    public void PickupItem(PlayerPickupItemEvent e)
    {
        if(e.getPlayer().getOpenInventory().getType() == InventoryType.ANVIL)
        {
            if(e.getItem().getItemStack().getType() == Material.MOB_SPAWNER)
            {
                e.setCancelled(true);
            }
        }
    }

Errors:

Code:

[00:44:28 ERROR]: Could not pass event InventoryOpenEvent to MobSpawner v1.0
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:302) ~[craftbukki
t.jar:git-Bukkit-e91aed8]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[craftbukkit.
jar:git-Bukkit-e91aed8]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:501) [craftbukki
t.jar:git-Bukkit-e91aed8]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:486) [craftbukki
t.jar:git-Bukkit-e91aed8]
        at org.bukkit.craftbukkit.v1_8_R3.event.CraftEventFactory.callInventoryOpenEvent(CraftEventF
actory.java:698) [craftbukkit.jar:git-Bukkit-e91aed8]
        at org.bukkit.craftbukkit.v1_8_R3.event.CraftEventFactory.callInventoryOpenEvent(CraftEventF
actory.java:684) [craftbukkit.jar:git-Bukkit-e91aed8]
        at net.minecraft.server.v1_8_R3.EntityPlayer.openTileEntity(EntityPlayer.java:621) [craftbuk
kit.jar:git-Bukkit-e91aed8]
        at net.minecraft.server.v1_8_R3.BlockAnvil.interact(SourceFile:58) [craftbukkit.jar:git-Bukk
it-e91aed8]
        at net.minecraft.server.v1_8_R3.PlayerInteractManager.interact(PlayerInteractManager.java:49
5) [craftbukkit.jar:git-Bukkit-e91aed8]
        at net.minecraft.server.v1_8_R3.PlayerConnection.a(PlayerConnection.java:705) [craftbukkit.j
ar:git-Bukkit-e91aed8]
        at net.minecraft.server.v1_8_R3.PacketPlayInBlockPlace.a(PacketPlayInBlockPlace.java:52) [cr
aftbukkit.jar:git-Bukkit-e91aed8]
        at net.minecraft.server.v1_8_R3.PacketPlayInBlockPlace.a(PacketPlayInBlockPlace.java:1) [cra
ftbukkit.jar:git-Bukkit-e91aed8]
        at net.minecraft.server.v1_8_R3.PlayerConnectionUtils$1.run(SourceFile:13) [craftbukkit.jar:
git-Bukkit-e91aed8]
        at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_45]
        at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_45]
        at net.minecraft.server.v1_8_R3.SystemUtils.a(SystemUtils.java:19) [craftbukkit.jar:git-Bukk
it-e91aed8]
        at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:676) [craftbukkit.jar
:git-Bukkit-e91aed8]
        at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:335) [craftbukkit.jar
:git-Bukkit-e91aed8]
        at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:632) [craftbukkit.jar
:git-Bukkit-e91aed8]
        at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:540) [craftbukkit.j
ar:git-Bukkit-e91aed8]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_45]
Caused by: java.lang.NullPointerException
        at me.NortherKnight.MobSpawner.onInventoryOpenEvent(MobSpawner.java:91) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_45]
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_45]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_45]
        at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_45]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:300) ~[craftbukki
t.jar:git-Bukkit-e91aed8]

This errors happen when another player throws a spawner at the player that is in the anvil.

Solved it the for loop in onInventoryOpenEvent was not necessary i just did:

Code:

if(e.getPlayer().getInventory().contains(Material.MOB_SPAWNER)
{
      e.setCancelled(true);
}

EDIT by Moderator: merged posts, please use the edit button instead of double posting.