Fix PlayerTrade/PurchaseEvent visual issue when being cancelled

[HaHaWTH]

This pull request fixes #11693.

Changes made

Fixes client-side visual issues when cancelling PlayerTradeEvent/PlayerPurchaseEvent by resending merchant offer packets.

To reproduce

Make a plugin that cancels PlayerTradeEvent like this code snippet:

@EventHandler
 public void onPlayerTrade(PlayerTradeEvent event) {
      event.setCancelled(true);
      event.setRewardExp(false);
      event.setIncreaseTradeUses(false);
 }