Liquid tanks 1.13.1

[18:36:18] [Server thread/ERROR]: Error occurred while disabling LiquidTanks v2.0.1 (Is it up to date?)
java.lang.NullPointerException: null
	at net.arcaniax.liquidtanks.Main.onDisable(Main.java:24) ~[?:?]
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:266) ~[patched_1.13.1.jar:git-Paper-192]
	at org.bukkit.plugin.java.JavaPluginLoader.disablePlugin(JavaPluginLoader.java:359) ~[patched_1.13.1.jar:git-Paper-192]
	at org.bukkit.plugin.java.JavaPluginLoader.disablePlugin(JavaPluginLoader.java:342) ~[patched_1.13.1.jar:git-Paper-192]
	at net.arcaniax.liquidtanks.nms.NmsManager.<init>(NmsManager.java:28) ~[?:?]
	at net.arcaniax.liquidtanks.Main.onEnable(Main.java:16) ~[?:?]
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:264) ~[patched_1.13.1.jar:git-Paper-192]
	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:325) ~[patched_1.13.1.jar:git-Paper-192]
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:405) ~[patched_1.13.1.jar:git-Paper-192]
	at org.bukkit.craftbukkit.v1_13_R2.CraftServer.enablePlugin(CraftServer.java:434) ~[patched_1.13.1.jar:git-Paper-192]
	at org.bukkit.craftbukkit.v1_13_R2.CraftServer.enablePlugins(CraftServer.java:348) ~[patched_1.13.1.jar:git-Paper-192]
	at net.minecraft.server.v1_13_R2.MinecraftServer.l(MinecraftServer.java:613) ~[patched_1.13.1.jar:git-Paper-192]
	at net.minecraft.server.v1_13_R2.MinecraftServer.a(MinecraftServer.java:576) ~[patched_1.13.1.jar:git-Paper-192]
	at net.minecraft.server.v1_13_R2.MinecraftServer.a(MinecraftServer.java:433) ~[patched_1.13.1.jar:git-Paper-192]
	at net.minecraft.server.v1_13_R2.DedicatedServer.init(DedicatedServer.java:305) ~[patched_1.13.1.jar:git-Paper-192]
	at net.minecraft.server.v1_13_R2.MinecraftServer.run(MinecraftServer.java:784) ~[patched_1.13.1.jar:git-Paper-192]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_151]
[18:36:18] [Server thread/ERROR]: Error occurred while enabling LiquidTanks v2.0.1 (Is it up to date?)
org.bukkit.plugin.IllegalPluginAccessException: Plugin attempted to register task while disabled
	at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftScheduler.validate(CraftScheduler.java:488) ~[patched_1.13.1.jar:git-Paper-192]
	at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftScheduler.runTaskTimer(CraftScheduler.java:150) ~[patched_1.13.1.jar:git-Paper-192]
	at net.arcaniax.liquidtanks.tank.LiquidTank.gameLoop(LiquidTank.java:86) ~[?:?]
	at net.arcaniax.liquidtanks.TankManager.<init>(TankManager.java:57) ~[?:?]
	at net.arcaniax.liquidtanks.Main.onEnable(Main.java:18) ~[?:?]
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:264) ~[patched_1.13.1.jar:git-Paper-192]
	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:325) ~[patched_1.13.1.jar:git-Paper-192]
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:405) ~[patched_1.13.1.jar:git-Paper-192]
	at org.bukkit.craftbukkit.v1_13_R2.CraftServer.enablePlugin(CraftServer.java:434) ~[patched_1.13.1.jar:git-Paper-192]
	at org.bukkit.craftbukkit.v1_13_R2.CraftServer.enablePlugins(CraftServer.java:348) ~[patched_1.13.1.jar:git-Paper-192]
	at net.minecraft.server.v1_13_R2.MinecraftServer.l(MinecraftServer.java:613) ~[patched_1.13.1.jar:git-Paper-192]
	at net.minecraft.server.v1_13_R2.MinecraftServer.a(MinecraftServer.java:576) ~[patched_1.13.1.jar:git-Paper-192]
	at net.minecraft.server.v1_13_R2.MinecraftServer.a(MinecraftServer.java:433) ~[patched_1.13.1.jar:git-Paper-192]
	at net.minecraft.server.v1_13_R2.DedicatedServer.init(DedicatedServer.java:305) ~[patched_1.13.1.jar:git-Paper-192]
	at net.minecraft.server.v1_13_R2.MinecraftServer.run(MinecraftServer.java:784) ~[patched_1.13.1.jar:git-Paper-192]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_151]