Fix in stock calculation. closes #118

prototype/src/main/java/org/hso/ecommerce/controller/shop/ShopArticleController.java

@@ -52,7 +52,11 @@ public class ShopArticleController {
         }
         model.addAttribute("article", article);
 
-        if (warehouseBookingPositionSlotEntryRepository.getByArticle(id).get(0).newSumSlot > 0) {   //check if in Stock
+        if (warehouseBookingPositionSlotEntryRepository
+                .getByArticle(id)
+                .stream()
+                .mapToInt(e -> e.newSumSlot)
+                .sum() > 0) {   //check if in Stock
             model.addAttribute("inStock", true);
         } else {
             model.addAttribute("inStock", false);