Merge pull request #1173 from torresgol10/master

The dataprovider method is missing arguments when it is an option group.

dist/js/bootstrap-multiselect.js

@@ -1777,6 +1777,7 @@
                             value: subOption.value,
                             label: subOption.label !== undefined && subOption.label !== null ? subOption.label : subOption.value,
                             title: subOption.title,
+                            class: subOption.class,
                             selected: !!subOption.selected,
                             disabled: !!subOption.disabled
                         };