Empty commands shall not be dispatched

Fixes PaperMC/Paper#5018.

Spigot-Server-Patches/0647-Empty-commands-shall-not-be-dispatched.patch

@@ -0,0 +1,18 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Mariell Hoversholm <proximyst@proximyst.com>
+Date: Wed, 6 Jan 2021 23:38:43 +0100
+Subject: [PATCH] Empty commands shall not be dispatched
+
+
+diff --git a/src/main/java/net/minecraft/server/CommandDispatcher.java b/src/main/java/net/minecraft/server/CommandDispatcher.java
+index 22d748008d24fd6ed7cd8c4914e2ceb378f32c95..e56ff365118c50486f36cb15a4ca062c5a481674 100644
+--- a/src/main/java/net/minecraft/server/CommandDispatcher.java
++++ b/src/main/java/net/minecraft/server/CommandDispatcher.java
+@@ -139,6 +139,7 @@ public class CommandDispatcher {
+         command = event.getCommand();
+ 
+         String[] args = command.split(" ");
++        if (args.length == 0) return 0; // Paper - empty commands shall not be dispatched
+ 
+         String cmd = args[0];
+         if (cmd.startsWith("minecraft:")) cmd = cmd.substring("minecraft:".length());