java.lang.NullPointerException: Exception in server tick loop
    at moze_intel.projecte.gameObjs.container.inventory.TransmuteTabletInventory.func_70305_f(TransmuteTabletInventory.java:389)
    at moze_intel.projecte.gameObjs.container.TransmuteTabletContainer.func_75134_a(TransmuteTabletContainer.java:137)
    at net.minecraft.entity.player.EntityPlayer.func_70106_y(EntityPlayer.java:1325)
    at net.minecraft.world.World.func_72900_e(World.java:1371)
    at net.minecraft.server.management.ServerConfigurationManager.func_72367_e(ServerConfigurationManager.java:316)
    at net.minecraft.network.NetHandlerPlayServer.func_147231_a(NetHandlerPlayServer.java:633)
    at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:154)
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:659)
    at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:334)
    at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427)
    at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)