[19:31:01] [Server thread/WARN]: java.lang.NullPointerException
[19:31:01] [Server thread/WARN]:        at me.mrCookieSlime.CSCoreLibPlugin.general.Inventory.CustomBookOverlay.lambda$open$0(CustomBookOverlay.java:142)
[19:31:01] [Server thread/WARN]:        at org.bukkit.craftbukkit.v1_14_R1.scheduler.CraftTask.run(CraftTask.java:81)
[19:31:01] [Server thread/WARN]:        at org.bukkit.craftbukkit.v1_14_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:394)
[19:31:01] [Server thread/WARN]:        at net.minecraft.server.v1_14_R1.MinecraftServer.b(MinecraftServer.java:1008)
[19:31:01] [Server thread/WARN]:        at net.minecraft.server.v1_14_R1.DedicatedServer.b(DedicatedServer.java:396)
[19:31:01] [Server thread/WARN]:        at net.minecraft.server.v1_14_R1.MinecraftServer.a(MinecraftServer.java:956)
[19:31:01] [Server thread/WARN]:        at net.minecraft.server.v1_14_R1.MinecraftServer.run(MinecraftServer.java:801)
[19:31:01] [Server thread/WARN]:        at java.lang.Thread.run(Unknown Source)