Hotfix: Allow pets to be purchased from shops again

Variant_id needs to be set to null (or "none") if it's not set otherwise it errors when purchasing from shops

app/Services/PetManager.php

@@ -516,7 +516,7 @@ public function editCustomImageDescription($pet, $data) {
      *
      * @return bool
      */
-    public function creditPet($sender, $recipient, $type, $data, $pet, $quantity, $variant_id) {
+    public function creditPet($sender, $recipient, $type, $data, $pet, $quantity, $variant_id = null) {
         DB::beginTransaction();
 
         try {