Do not lose stack information in case of server overload command termination

src/de/steamwar/lobby/portal/CommandPortal.java

@@ -28,7 +28,7 @@ import de.steamwar.sql.SteamwarUser;
 import org.bukkit.Location;
 import org.bukkit.entity.Player;
 
-import java.util.Deque;
+import java.util.Iterator;
 import java.util.Map;
 import java.util.logging.Level;
 
@@ -56,16 +56,16 @@ public class CommandPortal implements PortalHandler {
                 maxId = stackIds[i-1];
         }
 
-        Deque<Portal> stack = Portals.getStack(player);
+        Iterator<Portal> stack = Portals.getStack(player).iterator();
         String[] pieces = new String[stackIds.length];
         while (maxId > 0) {
-            if(stack.isEmpty()) {
+            if(!stack.hasNext()) {
                 LobbySystem.getPlugin().getLogger().log(Level.WARNING, "Stackportal with missing elements: " + player.getName() + " /" + command);
                 player.sendMessage("§cEigentlich solltest du gerade gar nicht durch dieses Portal durchgehen können...");
                 return;
             }
 
-            Portal portal = stack.pop();
+            Portal portal = stack.next();
             if(portal.type() == PortalType.STACK) {
                 for(int i = 0; i < stackIds.length; i++) {
                     if(stackIds[i] == maxId) {