Fix #207 set pet owner when for has an error

src/main/java/org/springframework/samples/petclinic/owner/PetController.java

@@ -103,6 +103,7 @@ class PetController {
     @RequestMapping(value = "/pets/{petId}/edit", method = RequestMethod.POST)
     public String processUpdateForm(@Valid Pet pet, BindingResult result, Owner owner, ModelMap model) {
         if (result.hasErrors()) {
+            pet.setOwner(owner);
             model.put("pet", pet);
             return VIEWS_PETS_CREATE_OR_UPDATE_FORM;
         } else {