fix: consider case in onQuiqqerOrderBasketRemovePos where article does not exist

(cherry picked from commit 017e2453)

src/QUI/ERP/Coupons/Events.php

@@ -159,6 +159,11 @@ public static function onQuiqqerOrderBasketRemovePos(
 
 
         $Article = $Order->getArticles()->getArticle($pos);
+
+        if (!$Article) {
+            return;
+        }
+
         $customData = $Article->getCustomData();
         $orderCoupons = $Order->getDataEntry('quiqqer-coupons');