Do not use worldgen executor for api profile completions

We cannot put blocking network I/O onto the worldgen threads,
this will crash the server if it stalls

patches/server/0564-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/commands/Commands.java b/src/main/java/net/minecraft/commands/Commands.java
+index a8f3a84615a640d2949d268ef1ac81a051f5a38b..2dc41adc4e915f98451d79f0826b75560b716d21 100644
+--- a/src/main/java/net/minecraft/commands/Commands.java
++++ b/src/main/java/net/minecraft/commands/Commands.java
+@@ -236,6 +236,7 @@ public class Commands {
+         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());