Merge branch 'dev'

backend/controllers/DistributionController.php

             'id_distribution' => $idDistribution,
             'id_product' => $idProduct,
         ]) ;
-        $productDistribution->quantity_max = (int) $quantityMax ;
+        
+        $productDistribution->quantity_max = (!$quantityMax) ? null : (int) $quantityMax ;
+        
         $productDistribution->save() ;
         
         return ['success'] ;