Array flip makes voucher strings to int (#161)

* Update Rule.php

Sometimes legacy data could trigger an exception because of null-values.

* [bugfix] cast because of stronger typing

When adding voucher-tokens that are all numbers the array_flip function will make then int's so we need to cast to string in OrderManager.
We also need to cast to int when reading configuration->getUsages() because it returns string.

* Revert "Update Rule.php"

This reverts commit 309e6ad.

src/OrderManager/V7/OrderManager.php

@@ -708,7 +708,7 @@ protected function applyVoucherTokens(AbstractOrder $order, CartInterface $cart)
 
             //add new tokens - which are the remaining entries of $flippedVoucherTokens
             foreach ($flippedVoucherTokens as $code => $x) {
-                $this->voucherService->applyToken($code, $cart, $order);
+                $this->voucherService->applyToken((string)$code, $cart, $order);
             }
         }
     }

src/VoucherService/TokenManager/Single.php

@@ -208,7 +208,7 @@ public function reserveToken(string $code, CartInterface $cart): bool
     public function applyToken(string $code, CartInterface $cart, AbstractOrder $order): OnlineShopVoucherToken|bool
     {
         if ($token = Token::getByCode($code)) {
-            if ($token->check($this->configuration->getUsages(), true)) {
+            if ($token->check((int)$this->configuration->getUsages(), true)) {
                 if ($token->apply()) {
                     $orderToken = \Pimcore\Model\DataObject\OnlineShopVoucherToken::getByToken($code, 1);
                     if (!$orderToken instanceof \Pimcore\Model\DataObject\OnlineShopVoucherToken) {