Game freezing and crashing when I open GUI.

So, I finally made my GUI and when I right-click on the block that opens said GUI, the game completely freezes (stops responding) for maybe 5 seconds, then closes.

I tried the solution given under other posts about this and nothing worked. Any help? (Here is the crash log)

---- Minecraft Crash Report ----
// Don't be sad, have a hug! <3

Time: 2020.01.02. 17:33
Description: Ticking entity

java.lang.ArrayIndexOutOfBoundsException: 5
    at java.util.Arrays$ArrayList.get(Arrays.java:3841) ~[?:1.8.0_51] {}
    at net.minecraft.util.NonNullList.get(SourceFile:46) ~[?:?] {}
    at net.mcreator.crafting_mod.MCreatorMortar$CustomTileEntity.func_70301_a(MCreatorMortar.java:219) ~[?:?] {}
    at net.minecraft.inventory.container.Slot.func_75211_c(Slot.java:54) ~[?:?] {}
    at net.minecraft.inventory.container.Container.func_75142_b(Container.java:116) ~[?:?] {}
    at net.minecraft.entity.player.ServerPlayerEntity.func_70071_h_(ServerPlayerEntity.java:321) ~[?:?] {pl:accesstransformer:B}
    at net.minecraft.world.server.ServerWorld.func_217479_a(ServerWorld.java:587) ~[?:?] {}
    at net.minecraft.world.server.ServerWorld$$Lambda$3645/2114690706.accept(Unknown Source) ~[?:?] {}
    at net.minecraft.world.World.func_217390_a(World.java:684) ~[?:?] {pl:accesstransformer:B}
    at net.minecraft.world.server.ServerWorld.func_72835_b(ServerWorld.java:394) ~[?:?] {}
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:829) ~[?:?] {pl:accesstransformer:B}
    at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:764) ~[?:?] {pl:accesstransformer:B}
    at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:112) ~[?:?] {pl:runtimedistcleaner:A}
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:622) [?:?] {pl:accesstransformer:B}
    at java.lang.Thread.run(Thread.java:745) [?:1.8.0_51] {}

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

-- Head --
Thread: Server thread
Stacktrace:
    at java.util.Arrays$ArrayList.get(Arrays.java:3841)
    at net.minecraft.util.NonNullList.get(SourceFile:46)
    at net.mcreator.crafting_mod.MCreatorMortar$CustomTileEntity.func_70301_a(MCreatorMortar.java:219)
    at net.minecraft.inventory.container.Slot.func_75211_c(Slot.java:54)
    at net.minecraft.inventory.container.Container.func_75142_b(Container.java:116)
    at net.minecraft.entity.player.ServerPlayerEntity.func_70071_h_(ServerPlayerEntity.java:321)
    at net.minecraft.world.server.ServerWorld.func_217479_a(ServerWorld.java:587)
    at net.minecraft.world.server.ServerWorld$$Lambda$3645/2114690706.accept(Unknown Source)

-- Entity being ticked --
Details:
    Entity Type: minecraft:player (net.minecraft.entity.player.ServerPlayerEntity)
    Entity ID: 263
    Entity Name: davtov
    Entity's Exact location: 236.62, 67.00, -104.69
    Entity's Block location: World: (236,67,-105), Chunk: (at 12,4,7 in 14,-7; contains blocks 224,0,-112 to 239,255,-97), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
    Entity's Momentum: 0.00, -0.08, 0.00
    Entity's Passengers: []
    Entity's Vehicle: ~~ERROR~~ NullPointerException: null
Stacktrace:
    at net.minecraft.world.World.func_217390_a(World.java:684)
    at net.minecraft.world.server.ServerWorld.func_72835_b(ServerWorld.java:394)

-- Affected level --
Details:
    All players: 1 total; [ServerPlayerEntity['davtov'/263, l='Új föld', x=236.62, y=67.00, z=-104.69]]
    Chunk stats: ServerChunkCache: 2851
    Level dimension: DimensionType{minecraft:overworld}
    Level name: Új föld
    Level seed: 6606657633495383587
    Level generator: ID 00 - default, ver 1. Features enabled: true
    Level generator options: {}
    Level spawn location: World: (256,63,-31), Chunk: (at 0,3,1 in 16,-2; contains blocks 256,0,-32 to 271,255,-17), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
    Level time: 4058 game time, 4058 day time
    Level storage version: 0x04ABD - Anvil
    Level weather: Rain time: 150300 (now: false), thunder time: 68005 (now: false)
    Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:829)
    at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:764)
    at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:112)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:622)
    at java.lang.Thread.run(Thread.java:745)

-- System Details --
Details:
    Minecraft Version: 1.14.4
    Minecraft Version ID: 1.14.4
    Operating System: Windows 10 (amd64) version 10.0
    Java Version: 1.8.0_51, Oracle Corporation
    Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
    Memory: 1130778256 bytes (1078 MB) / 2147483648 bytes (2048 MB) up to 2147483648 bytes (2048 MB)
    CPUs: 12
    JVM Flags: 9 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
    ModLauncher: 3.2.0+60+b86c1d4
    ModLauncher launch target: fmlclient
    ModLauncher naming: srg
    ModLauncher services: 
        /eventbus-1.0.0-service.jar eventbus PLUGINSERVICE 
        /forge-1.14.4-28.1.0.jar object_holder_definalize PLUGINSERVICE 
        /forge-1.14.4-28.1.0.jar runtime_enum_extender PLUGINSERVICE 
        /accesstransformers-1.0.0-shadowed.jar accesstransformer PLUGINSERVICE 
        /forge-1.14.4-28.1.0.jar capability_inject_definalize PLUGINSERVICE 
        /forge-1.14.4-28.1.0.jar runtimedistcleaner PLUGINSERVICE 
        /forge-1.14.4-28.1.0.jar fml TRANSFORMATIONSERVICE 
    FML: 28.1
    Forge: net.minecraftforge:28.1.0
    FML Language Providers: 
        javafml@28.1
        minecraft@1
    Mod List: 
        beta15.jar Crafting Mod {crafting_mod@1.0.0 DONE}
        forge-1.14.4-28.1.0-universal.jar Forge {forge@28.1.0 DONE}
        forge-1.14.4-28.1.0-client.jar Minecraft {minecraft@1.14.4 DONE}
    Player Count: 1 / 8; [ServerPlayerEntity['davtov'/263, l='Új föld', x=236.62, y=67.00, z=-104.69]]
    Data Packs: vanilla, mod:forge, mod:crafting_mod
    Type: Integrated Server (map_client.txt)
    Is Modded: Definitely; Client brand changed to 'forge'