Support filter with clickable opt groups.

dist/js/bootstrap-multiselect.js

@@ -585,10 +585,11 @@
 
                     // Search all option in optgroup
                     var $options = group.nextUntil('li.multiselect-group');
+                    var $visibleOptions = $options.filter(":visible");
 
                     // check or uncheck items
                     var allChecked = true;
-                    var optionInputs = $options.find('input');
+                    var optionInputs = $visibleOptions.find('input');
                     optionInputs.each(function() {
                         allChecked = allChecked && $(this).prop('checked');
                     });

index.html

@@ -1711,6 +1711,44 @@
         });
     });
 </script>
+</pre>
+                                    </div>
+                                    
+                                    <p>
+                                        Clickable <code>optgroup</code>'s are also supported:
+                                    </p>
+                                    <div class="example">
+                                        <script type="text/javascript">
+                                            $(document).ready(function() {
+                                                $('#example-enableFiltering-enableClickableOptGroups').multiselect({
+                                                    enableFiltering: true,
+                                                    enableClickableOptGroups: true
+                                                });
+                                            });
+                                        </script>
+                                        <select id="example-enableFiltering-enableClickableOptGroups" multiple="multiple">
+                                            <optgroup label="Group 1">
+                                                <option value="1-1">Option 1.1</option>
+                                                <option value="1-2" selected="selected">Option 1.2</option>
+                                                <option value="1-3" selected="selected">Option 1.3</option>
+                                            </optgroup>
+                                            <optgroup label="Group 2">
+                                                <option value="2-1">Option 2.1</option>
+                                                <option value="2-2">Option 2.2</option>
+                                                <option value="2-3">Option 2.3</option>
+                                            </optgroup>
+                                        </select>
+                                    </div>
+                                    <div class="highlight">
+<pre class="prettyprint linenums">
+&lt;script type=&quot;text/javascript&quot;&gt;
+    $(document).ready(function() {
+        $('#example-example-enableFiltering-enableClickableOptgroups').multiselect({
+            enableFiltering: true,
+            enableClickableOptGroups: true
+        });
+    });
+&lt;/script&gt;
 </pre>
                                     </div>
                                 </td>