fix

alkatorapi/views.py

@@ -350,20 +350,20 @@ def products(request):
 def cart_add(request):
     _id = request.GET['id']
     user = request.user
-    if not user.cart:
+    try:
+        user.cart
+    except User.cart.RelatedObjectDoesNotExist:
         cart = Cart(user=user)
         cart.save()
-    else:
-        cart = user.cart
     try:
         cart_product = CartProduct(
             product=Product.objects.get(id=_id),
-            cart=cart,
+            cart=user.cart,
             quantity=1,
         )
         cart_product.save()
     except IntegrityError as e:
-            return HttpResponse('{"status":"failed", "reason":"Předmět už v košíku je!"}', content_type='application/json')
+            return HttpResponse('{"status":"failed", "reason":"Předmět už v košíku je!"}', status=400, content_type='application/json')
     return HttpResponse('{"status":"success", "reason":"Úspěšně přidáno do košíku."}', status=200)