Don't run command blocks in empty worlds. Fixes BUKKIT-3094

src/main/java/net/minecraft/server/TileEntityCommand.java

@@ -25,7 +25,7 @@ public class TileEntityCommand extends TileEntity implements ICommandListener {
             MinecraftServer minecraftserver = MinecraftServer.getServer();
 
             if (minecraftserver != null && minecraftserver.getEnableCommandBlock()) {
-                // CraftBukkit start - handle command block as console TODO: add new CommandSender for this
+                // CraftBukkit start - handle command block as console
                 org.bukkit.command.SimpleCommandMap commandMap = minecraftserver.server.getCommandMap();
                 Joiner joiner = Joiner.on(" ");
                 String command = this.a;
@@ -47,6 +47,11 @@ public class TileEntityCommand extends TileEntity implements ICommandListener {
                     return;
                 }
 
+                // if the world has no players don't run
+                if (this.world.players.isEmpty()) {
+                    return;
+                }
+
                 commands.add(args);
 
                 // find positions of command block syntax, if any