MythicMobs Full Error (?)

[21:26:41 WARN]: [MythicMobs] ✗ Config Error for Mob 'Citizen_tools_weapons' in 'NPCs.yml': A villager trade is configured incorrectly.
[21:26:41 WARN]: java.lang.NullPointerException
[21:26:41 WARN]:        at org.bukkit.inventory.ItemStack.<init>(ItemStack.java:72)
[21:26:41 WARN]:        at org.bukkit.inventory.ItemStack.<init>(ItemStack.java:50)
[21:26:41 WARN]:        at io.lumine.xikage.mythicmobs.adapters.bukkit.BukkitItemStack.<init>(BukkitItemStack.java:42)
[21:26:41 WARN]:        at io.lumine.xikage.mythicmobs.adapters.bukkit.entities.BukkitVillager.instantiate(BukkitVillager.java:96)
[21:26:41 WARN]:        at io.lumine.xikage.mythicmobs.mobs.MythicMob.<init>(MythicMob.java:239)
[21:26:41 WARN]:        at io.lumine.xikage.mythicmobs.mobs.MobManager.loadMobs(MobManager.java:162)
[21:26:41 WARN]:        at io.lumine.xikage.mythicmobs.io.ConfigManager.LoadAll(ConfigManager.java:97)
[21:26:41 WARN]:        at io.lumine.xikage.mythicmobs.commands.ReloadCommand.onCommand(ReloadCommand.java:29)
[21:26:41 WARN]:        at io.lumine.utils.commands.Command.onCommand(Command.java:69)
[21:26:41 WARN]:        at io.lumine.utils.commands.Command.onCommand(Command.java:60)
[21:26:41 WARN]:        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44)
[21:26:41 WARN]:        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:152)
[21:26:41 WARN]:        at org.bukkit.craftbukkit.v1_12_R1.CraftServer.dispatchCommand(CraftServer.java:685)
[21:26:41 WARN]:        at org.bukkit.craftbukkit.v1_12_R1.CraftServer.dispatchServerCommand(CraftServer.java:648)
[21:26:41 WARN]:        at net.minecraft.server.v1_12_R1.DedicatedServer.aP(DedicatedServer.java:463)
[21:26:41 WARN]:        at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:424)
[21:26:41 WARN]:        at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:774)
[21:26:41 WARN]:        at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:666)