Bukkit

What steps will reproduce the problem?
1.
2.
3.

What is the expected output? What do you see instead?
Convert backpack ownership when throwing out of inventory

What version of the product are you using?
RB 1.6.4

Do you have an error log of what happened?
[12:39:35] [Server thread/ERROR]: Could not pass event PlayerPickupItemEvent to RealisticBackpacks v1.6.4
org.bukkit.event.EventException
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:427) ~[craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:481) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:466) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.EntityItem.b_(EntityItem.java:250) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.EntityHuman.r(EntityHuman.java:445) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.EntityHuman.e(EntityHuman.java:437) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.EntityLiving.h(EntityLiving.java:1299) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.EntityHuman.h(EntityHuman.java:162) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.EntityPlayer.i(EntityPlayer.java:240) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.PlayerConnection.a(PlayerConnection.java:342) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at com.bergerkiller.bukkit.common.internal.network.CommonPacketHandler$CommonPlayerConnection.a(CommonPacketHandler.java:280) [BKCommonLib-1.57.jar:?]
    at net.minecraft.server.v1_7_R1.PacketPlayInFlying.a(SourceFile:137) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.PacketPlayInFlying.handle(SourceFile:8) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.NetworkManager.a(NetworkManager.java:146) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.ServerConnection.c(SourceFile:134) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:655) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:250) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:545) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:457) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
Caused by: java.lang.NullPointerException
    at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source) ~[?:1.7.0_45]
    at java.lang.Float.parseFloat(Unknown Source) ~[?:1.7.0_45]
    at org.fatecrafters.plugins.listeners.PlayerListener.onPickup(PlayerListener.java:168) ~[?:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_45]
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_45]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_45]
    at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.7.0_45]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425) ~[craftbukkit-1.7.2-R0.2.jar:git-Bukkit-1.7.2-R0.2-b2974jnks]
    ... 20 more

Please provide any additional information below.
  Keyring:
    Size: 9
    addGlow: false
    OpenWith: left_click
    Purchasable: true
    Price: 0
    UseRecipe: false
    Override: '0'
    BackpackItem:
      id: '131'
      name: '&aKey Ring'
      lore:
      - '&cYou put keys on it.'
    UseWhitelist: true
    ItemWhitelist:
    - 369
    - 280
    onDeath:
      dropContents: false
      destroyContents: false
      dropBackpack: false
      keepBackpack: true
    WalkSpeedFeature:
      enabled: false
    IncreasedHungerFeature:
      enabled: false

With keepBackpack true and everything else false it prevents the backpack from switching users when dropped on purpouse and generates that error if you try to trade it.