title: Why bootstrap-multiselect closes the dropdown-menu?
body: <p>In a nav-bar I have a dropdown-menu, in which I occupy bootstrap-multiselect.
  When I occupy a normal select it works fine, but I integrate the bootstrap-multiselect and closes the dropdown-menu</p>
  
  <p>I work in codeigniter, I load the multiselect with a getJSON function from an api, which works well with a normal select</p>
  
  <p>this is the html code</p>
  
  <pre class="lang-html prettyprint-override"><code>    &lt;nav class="navbar navbar-default navbar-expand-lg navbar-light navbar-fixed-top"&gt;
  
              &lt;ul class="nav navbar-nav navbar-right ml-auto"&gt;
                  &lt;li class="nav-item"&gt;
                      &lt;a id="btn_navbar" href="#" data-toggle="dropdown"
                          class="btn btn-primary dropdown-toggle get-started-btn mt-1 mb-1"&gt;Button&lt;/a&gt;
                      &lt;ul class="dropdown-menu form-wrapper"&gt;
                          &lt;li&gt;
                              &lt;form&gt;
                                  &lt;div class="form-group"&gt;
                                      &lt;label for="select_establecimiento"&gt;Colegio&lt;/label&gt;
                                      &lt;select class="form-control" id="select_establecimiento"&gt;
                                      &lt;/select&gt;
                                  &lt;/div&gt;
                                  &lt;div class="form-group"&gt;
                                      &lt;label for="select_mes"&gt;Mes&lt;/label&gt;
                                      &lt;select class="form-control" id="select_mes"&gt;
                                      &lt;/select&gt;
                                  &lt;/div&gt;
                                  &lt;div class="form-group"&gt;
                                      &lt;label for="select_periodo"&gt;Periodo&lt;/label&gt;
                                      &lt;select class="form-control" id="select_periodo"&gt;
                                      &lt;/select&gt;
                                  &lt;/div&gt;
                                  &lt;button id="change" class="btn btn-primary btn-md btn-block"&gt;Cambiar&lt;/button&gt;
                                  &lt;button id="logout" class="btn btn-info btn-md btn-block"&gt;Salir&lt;/button&gt;
                              &lt;/form&gt;
                          &lt;/li&gt;
                      &lt;/ul&gt;
                  &lt;/li&gt;
              &lt;/ul&gt;
          &lt;/div&gt;
      &lt;/nav&gt;
  </code></pre>
  
  <p>this is the javascript code</p>
  
  <pre><code>function select_establecimiento() {
      $.getJSON('get_establecimiento', function (result) {
          var mySelect = $('#select_establecimiento').empty();
          $.each(result.data, function (index, value) {
              mySelect.append(new Option(value.name, value.id));
          })
          mySelect.multiselect({
              buttonWidth: '100%',
              refresh: true
          });
      })
  }
  </code></pre>