Problem with form validation in my spring boot project - spring

Question

I was following the 'Spring in Action' book and was creating the TacoCloud application.
I added validation to the Taco class as shown below -
#Data
public class Taco {
#NotNull
#Size(min=5, message="Name must be at least 5 characters long")
private String name;
#Size(min=1, message="You must choose atleast 1 ingredient")
private List<String> ingredients;
}
Then, in the controller class I added code that enables user to customize their taco before placing an order -
#Slf4j
#Controller
#RequestMapping("/design")
public class DesignTacoController {
#GetMapping
public String showDesignForm(Model model) {
List<Ingredient> ingredients = Arrays.asList(
new Ingredient("FLTO", "Flour Tortilla", Type.WRAP),
new Ingredient("COTO", "Corn Tortilla", Type.WRAP),
new Ingredient("GRBF", "Ground Beef", Type.PROTEIN),
new Ingredient("CARN", "Carnitas", Type.PROTEIN),
new Ingredient("TMTO", "Diced Tomatoes", Type.VEGGIES),
new Ingredient("LETC", "Lettuce", Type.VEGGIES),
new Ingredient("CHED", "Cheddar", Type.CHEESE),
new Ingredient("JACK", "Monterrey Jack", Type.CHEESE),
new Ingredient("SLSA", "Salsa", Type.SAUCE),
new Ingredient("SRCR", "Sour Cream", Type.SAUCE));
Type[] types = Ingredient.Type.values();
for (Type type : types) {
model.addAttribute(type.toString().toLowerCase(),
ingredients.stream().filter(c -> c.getType() == type).collect(Collectors.toList()));
}
model.addAttribute("design", new Taco());
return "design-form";
}
#PostMapping
public String processCreation(#Valid Taco taco, Errors errors) {
if(errors.hasErrors()) {
return "design-form";
}
log.info("Taco " + taco);
return "redirect:/orders/current";
}
}
But, when I run the application and submit the form with errors, it gives the following output -
java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'design' available as request attribute
I am not being able to resolve this. Any help would be appreciated.