fix: handle invocation when no turtles are available

lua/CC Tweaked/tutel/tutel-host.lua

@@ -340,6 +340,11 @@ end
 registerConsoleCommand("clear", clearCommand)
 
 function turtlesCommand()
+    if #turtles == 0 then 
+        log.info("no turtles registered")
+        return
+    end
+    
     for i=0, #turtles, 1 do
         local turt = turtles[i]