Remember to return.

src/main/java/com/gmail/nossr50/commands/player/MctopCommand.java

@@ -126,12 +126,14 @@ public class MctopCommand implements CommandExecutor {
         // TODO: Localize messages
         if (mcMMO.queueManager.contains(sender.getName())) {
             sender.sendMessage(ChatColor.RED + "Please wait for your previous command to process");
+            return;
         }
 
         if (!mcMMO.queueManager.queue(new McTopAsync(page, query, sender))) {
-            sender.sendMessage(ChatColor.RED + "Queue is full");
+            sender.sendMessage(ChatColor.RED + "Unable to add to queue");
+            return;
         }
 
-        sender.sendMessage(ChatColor.YELLOW + "Calculating leaderboards...");
+        sender.sendMessage(ChatColor.YELLOW + "Calculating mcMMO leaderboards...");
     }
 }