Error

[20:43:09 ERROR]: Error occurred while enabling CheckLeaderboard v1.0-SNAPSHOT (Is it up to date?)
java.lang.NullPointerException: null
        at me.liondadev.KillManager.<init>(KillManager.java:19) ~[?:?]
        at me.liondadev.Cleaderboard.onEnable(Cleaderboard.java:15) ~[?:?]
        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:264) ~[spigot-1.12.2.jar:git-Spigot-79a30d7-acbc348]
        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:337) [spigot-1.12.2.jar:git-Spigot-79a30d7-acbc348]
        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:403) [spigot-1.12.2.jar:git-Spigot-79a30d7-acbc348]
        at org.bukkit.craftbukkit.v1_12_R1.CraftServer.enablePlugin(CraftServer.java:381) [spigot-1.12.2.jar:git-Spigot-79a30d7-acbc348]
        at org.bukkit.craftbukkit.v1_12_R1.CraftServer.enablePlugins(CraftServer.java:330) [spigot-1.12.2.jar:git-Spigot-79a30d7-acbc348]
        at net.minecraft.server.v1_12_R1.MinecraftServer.t(MinecraftServer.java:422) [spigot-1.12.2.jar:git-Spigot-79a30d7-acbc348]
        at net.minecraft.server.v1_12_R1.MinecraftServer.l(MinecraftServer.java:383) [spigot-1.12.2.jar:git-Spigot-79a30d7-acbc348]
        at net.minecraft.server.v1_12_R1.MinecraftServer.a(MinecraftServer.java:338) [spigot-1.12.2.jar:git-Spigot-79a30d7-acbc348]
        at net.minecraft.server.v1_12_R1.DedicatedServer.init(DedicatedServer.java:272) [spigot-1.12.2.jar:git-Spigot-79a30d7-acbc348]
        at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:545) [spigot-1.12.2.jar:git-Spigot-79a30d7-acbc348]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_241]