title: Required attribute with tag select doesn't work
body: <p>I tried with required="true" and with th:required="required" and using only required(this throws an error since i am using thymeleaf), added the empty value value="",but still doesn't work.I tried added value="dumb" and value="" for the second option tag, same...doesn't work and tried using bootstrap validator.When I submit the form I have an pop-up, if I press OK then form is submitted.
  I am using chrome and I have another form where I am using input + required and there it's working.
  Any help will be appreciated. Thanks!</p>
  
  <pre><code>&lt;form th:action="@{/appointment/create}" method="post" id="appointmentForm"&gt;
  &lt;div class="form-group"&gt;
                  &lt;label for="location"&gt;Alege institutia:&lt;/label&gt;
  
                  &lt;select class="form-control" required="required" 
                  th:value="${appointment.institutie}"name="institutie" 
                  id="institutie"&gt;
  
                   &lt;option value="" disabled="disabled" selected="selected" &gt; 
                   -- alege institutia --&lt;/option&gt;
                   &lt;option th:each="institutie : ${institutieList}"  
                 th:text="${institutie.numeInstitutie}" &gt;&lt;/option&gt;
  
                 &lt;/select&gt;
  &lt;/div&gt;&lt;/form&gt;
  
  
              var confirm = function() {
              bootbox.confirm({
                  title : "Confirmare programare",
                  message : "Doriti sa creeati programarea?",
                  buttons : {
                      cancel : {
                          label : '&lt;i class="fa fa-times"&gt;&lt;/i&gt; Nu'
                      },
                      confirm : {
                          label : '&lt;i class="fa fa-check"&gt;&lt;/i&gt; Da'
                      }
                  },
                  callback : function(result) {
                      if (result == true) {
                          $('#appointmentForm').submit();
                      } else {
                          console.log("Confirmare anulata.");
                      }
                  }
              });
          };
  </code></pre>
  
  <p>UPDATE 
  The controller which takes care to populate the "institutieList"</p>
  
  <pre><code>@RequestMapping(value="/create", method=RequestMethod.GET)
  public String createAppointmentPost(Model model, @ModelAttribute("city") 
  City city, @ModelAttribute("agency") Agency agency, Principal principal){
  
      User user = userService.findByUsername(principal.getName());
      Appointment appointment=new Appointment();
      model.addAttribute("appointment", appointment);
      model.addAttribute("dateString", "");
      model.addAttribute("cities", cityService.findAll());    
      model.addAttribute("institutieList", instituteService.findAll());
      model.addAttribute("myFiles", userService.listAllUploadedFiles(user));
      return "appointment";
  }   
  </code></pre>
  
  <p>UPDATE 2:
  The problem was with the submit button, I've forgot type="submit".</p>