Correctif mineur

Solver/Config/UnitSolver.php

 class UnitSolver
 {
 
-    public function getWeight(UnitInterface $unit, int $quantityProduct, int $quantity){
-        return ($quantityProduct / $unit->getCoefficient()) * $quantity;
+    public function getWeight(UnitInterface $unit, int $quantityProduct, ?int $quantity){
+        if($quantity) {
+            return ($quantityProduct / $unit->getCoefficient()) * $quantity;
+        }else{
+            $quantity = 0;
+        }
     }