title: th:if="${#fields.hasErrors()}" causes Exception evaluating SpringEL expression
body: <p>I'm trying to do validation on 1 field of the form as you guys can see:</p>
  
  <pre class="lang-html prettyprint-override"><code>&lt;div id ="EditModal" class="modal fade" role="dialog"&gt;
      &lt;form class="modal-dialog" th:action="@{/Edit}" th:object="${person1}" method="POST"&gt;
          &lt;div class="modal-content"&gt;
              &lt;div class="modal-header"&gt;
                  &lt;button type="button" class="close" data-dismiss="modal"&gt;&amp;times;&lt;/button&gt;
              &lt;/div&gt;
              &lt;div class="modal-body"&gt;
                  &lt;input type="hidden" id="edit-modal-person-id" name="id" value=""/&gt;
                  &lt;input type="text" placeholder="Name" id="edit-modal-person-name" name="name"/&gt;
                  &lt;p th:if="${#fields.hasErrors('name')}" th:errors="*{name}" th:class="'error'"&gt;something&lt;/p&gt;
                  &lt;div&gt;
                      &lt;a class="btn btn-default pull-right" id="PhoneNumberEdit"&gt;Edit Phone Number&lt;/a&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
              &lt;div class="modal-footer"&gt;
                  &lt;button type="submit" id="SubmitEdit" class="btn btn-default" &gt;Submit&lt;/button&gt;
                  &lt;button type="button" class = "btn btn-default" data-dismiss="modal"&gt;Cancel&lt;/button&gt;
              &lt;/div&gt;
          &lt;/div&gt;
      &lt;/form&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>the attribute <code>th:if="${#fields.hasErrors('name')}"</code> always causes the 500 error for me.</p>
  
  <p>my controller:</p>
  
  <pre><code>@RequestMapping(value = "/Edit", method = RequestMethod.POST)
  public String editPerson(@Valid @ModelAttribute(value="person1") PersonRequest person, BindingResult result) {
      if(result.hasErrors()) {
          return "redirect:All";
      }
      else {
          personService.update(person.getId(), person.getName());
          return "redirect:All";
      }
  }
  </code></pre>
  
  <p>my entity:</p>
  
  <pre><code>public class PersonRequest {
  
      @NotNull
      private long id;
  
      @NotEmpty
      @Name
      private String name;
  
      public long getId() {
          return id;
      }
      public void setId(long id) {
          this.id = id;
      }
      public String getName() {
          return name;
      }
      public void setName(String name) {
          this.name = name;
      }
      public PersonRequest() {
          super();
      }
  }
  </code></pre>
  
  <p>the console return this following error: </p>
  
  <pre><code>java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'person1' available as request attribute.
  </code></pre>
  
  <p>But I think that doesnt have anything to do with this because if I remove p tag it runs normally.</p>