TimingsCommand: fix missing type information for async task local storage

src/pocketmine/command/defaults/TimingsCommand.php

@@ -151,6 +151,7 @@ class TimingsCommand extends VanillaCommand{
 					}
 
 					public function onCompletion(Server $server){
+						/** @var CommandSender $sender */
 						$sender = $this->fetchLocal();
 						if($sender instanceof Player and !$sender->isOnline()){ // TODO replace with a more generic API method for checking availability of CommandSender
 							return;