--- app/code/DCKAP/Shoppinglist/Controller/Index/Ajaxshoppinglist.php (original)
+++ app/code/DCKAP/ShoppingList/Controller/Index/Ajaxshoppinglist.php (modified)
@@ -104,7 +104,10 @@
                                         ['shopping_list_item_id' => 'slitem.shopping_list_item_id']
                                     );
 
-            $shoppinglistCollection->getSelect()->where("slitem.product_id=".$productId);
+//added under improper error handling ADO 794671
+            if (!empty($productId) && is_numeric($productId)) {
+    $shoppinglistCollection->getSelect()->where("slitem.product_id=" . (int)$productId);
+}
             $results = $shoppinglistCollection->getData();
 
             $tempResult = [];