TodoList Error - 7/25/18

[23:58:57] [Server thread/INFO]: Diamond_Cat issued server command: /todo list
[23:58:57] [Server thread/ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'todo' in plugin ToDoList v1.0.1
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[patched_1.12.2.jar:git-Paper-1421]
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:151) ~[patched_1.12.2.jar:git-Paper-1421]
	at org.bukkit.craftbukkit.v1_12_R1.CraftServer.dispatchCommand(CraftServer.java:685) ~[patched_1.12.2.jar:git-Paper-1421]
	at net.minecraft.server.v1_12_R1.PlayerConnection.handleCommand(PlayerConnection.java:1472) ~[patched_1.12.2.jar:git-Paper-1421]
	at net.minecraft.server.v1_12_R1.PlayerConnection.a(PlayerConnection.java:1277) ~[patched_1.12.2.jar:git-Paper-1421]
	at net.minecraft.server.v1_12_R1.PacketPlayInChat.a(PacketPlayInChat.java:45) ~[patched_1.12.2.jar:git-Paper-1421]
	at net.minecraft.server.v1_12_R1.PacketPlayInChat.a(PacketPlayInChat.java:5) ~[patched_1.12.2.jar:git-Paper-1421]
	at net.minecraft.server.v1_12_R1.PlayerConnectionUtils.lambda$ensureMainThread$0(PlayerConnectionUtils.java:14) ~[patched_1.12.2.jar:git-Paper-1421]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_161]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_161]
	at net.minecraft.server.v1_12_R1.SystemUtils.a(SourceFile:46) [patched_1.12.2.jar:git-Paper-1421]
	at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:843) [patched_1.12.2.jar:git-Paper-1421]
	at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:427) [patched_1.12.2.jar:git-Paper-1421]
	at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:767) [patched_1.12.2.jar:git-Paper-1421]
	at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:665) [patched_1.12.2.jar:git-Paper-1421]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_161]
Caused by: java.lang.NullPointerException
	at com.electro2560.dev.todolist.commands.ToDoCommand.onCommand(ToDoCommand.java:51) ~[?:?]
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[patched_1.12.2.jar:git-Paper-1421]
	... 15 more