Undefined Item Problem?

One of my users on my server seems to be having a REALLY weird issue.

It seems to effect all of her chests - They all randomly have "Undefined Item" in them, ultimatly causing a crash.

I have no idea how this happened but it seems to be ONLY effecting her chests.

The "Undefined Item" has the sprite of a Mob Spawner.

This is the error anyone in the area of her chest is getting (keep in mind she broke the chest and now the nulled contents are on the ground)

Code:

03:44:46 [WARNING] Failed to handle packet: java.lang.NullPointerException
java.lang.NullPointerException
        at net.minecraft.server.ItemStack.d(ItemStack.java:95)
        at net.minecraft.server.ItemStack.f(ItemStack.java:103)
        at net.minecraft.server.InventoryPlayer.canHold(InventoryPlayer.java:124)
        at net.minecraft.server.EntityItem.b(EntityItem.java:205)
        at net.minecraft.server.EntityHuman.i(EntityHuman.java:212)
        at net.minecraft.server.EntityHuman.u(EntityHuman.java:204)
        at net.minecraft.server.EntityPlayer.u(EntityPlayer.java:205)
        at net.minecraft.server.EntityLiving.p_(EntityLiving.java:231)
        at net.minecraft.server.EntityHuman.p_(EntityHuman.java:90)
        at net.minecraft.server.EntityPlayer.a(EntityPlayer.java:162)
        at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:272)
        at net.minecraft.server.Packet10Flying.a(SourceFile:126)
        at net.minecraft.server.NetworkManager.a(NetworkManager.java:195)
        at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:74)
        at net.minecraft.server.NetworkListenThread.a(SourceFile:100)
        at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:370)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:285)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:394)

Right now anyone in the area just crashs with an "Internal Server Error"

Anyone have a solution?

 

i have the same problem on my single player, except my sprite is a fire block