Crash with a book

Hello im trying to develop a mod with custom dimensions and a book to guide the players, but everytime i open the gui it crashes
(Sorry about my bad english, im a brazillian)

---- Minecraft Crash Report ----
// Uh... Did I do that?

Time: 1/17/21 4:23 PM
Description: Ticking player

java.lang.NullPointerException: Ticking player
    at net.mcreator.badgesanddead.procedure.ProcedureAtt$1.getItemStack(ProcedureAtt.java:44)
    at net.mcreator.badgesanddead.procedure.ProcedureAtt.executeProcedure(ProcedureAtt.java:50)
    at net.mcreator.badgesanddead.procedure.ProcedureAtt.onPlayerTick(ProcedureAtt.java:219)
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_23_ProcedureAtt_onPlayerTick_PlayerTickEvent.invoke(.dynamic)
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
    at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182)
    at net.minecraftforge.fml.common.FMLCommonHandler.onPlayerPostTick(FMLCommonHandler.java:370)
    at net.minecraft.entity.player.EntityPlayer.updateSize(EntityPlayer.java:416)
    at net.minecraft.entity.player.EntityPlayer.onUpdate(EntityPlayer.java:326)
    at net.minecraft.entity.player.EntityPlayerMP.onUpdateEntity(EntityPlayerMP.java:423)
    at net.minecraft.network.NetHandlerPlayServer.update(NetHandlerPlayServer.java:185)
    at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher$1.update(NetworkDispatcher.java:212)
    at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:307)
    at net.minecraft.network.NetworkSystem.networkTick(NetworkSystem.java:197)
    at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:865)
    at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:743)
    at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:192)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:592)
    at java.lang.Thread.run(Thread.java:748)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Thread: Server thread
Stacktrace:
    at net.mcreator.badgesanddead.procedure.ProcedureAtt$1.getItemStack(ProcedureAtt.java:44)
    at net.mcreator.badgesanddead.procedure.ProcedureAtt.executeProcedure(ProcedureAtt.java:50)
    at net.mcreator.badgesanddead.procedure.ProcedureAtt.onPlayerTick(ProcedureAtt.java:219)
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_23_ProcedureAtt_onPlayerTick_PlayerTickEvent.invoke(.dynamic)
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
    at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182)
    at net.minecraftforge.fml.common.FMLCommonHandler.onPlayerPostTick(FMLCommonHandler.java:370)
    at net.minecraft.entity.player.EntityPlayer.updateSize(EntityPlayer.java:416)
    at net.minecraft.entity.player.EntityPlayer.onUpdate(EntityPlayer.java:326)

-- Player being ticked --
Details:
    Entity Type: null (net.minecraft.entity.player.EntityPlayerMP)
    Entity ID: 186
    Entity Name: Player531
    Entity's Exact location: -103.95, 63.00, -128.99
    Entity's Block location: World: (-104,63,-129), Chunk: (at 8,3,15 in -7,-9; contains blocks -112,0,-144 to -97,255,-129), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
    Entity's Momentum: 0.00, -0.08, 0.00
    Entity's Passengers: []
    Entity's Vehicle: ~~ERROR~~ NullPointerException: null
Stacktrace:
    at net.minecraft.entity.player.EntityPlayerMP.onUpdateEntity(EntityPlayerMP.java:423)
    at net.minecraft.network.NetHandlerPlayServer.update(NetHandlerPlayServer.java:185)
    at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher$1.update(NetworkDispatcher.java:212)
    at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:307)

-- Ticking connection --
Details:
    Connection: net.minecraft.network.NetworkManager@3718f484
Stacktrace:
    at net.minecraft.network.NetworkSystem.networkTick(NetworkSystem.java:197)
    at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:865)
    at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:743)
    at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:192)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:592)
    at java.lang.Thread.run(Thread.java:748)