use null instead of false in data that could be sent to api

assets/less/bootstrap/button-groups.less

@@ -59,7 +59,7 @@
     .border-right-radius(0);
   }
 }
-// Need .dropdown-toggle since :last-child doesn't apply, given that a .dropdown-menu is used immediately after it
+// Need .dropdown-toggle since :last-child doesn't apply given a .dropdown-menu immediately after it
 .btn-group > .btn:last-child:not(:first-child),
 .btn-group > .dropdown-toggle:not(:first-child) {
   .border-left-radius(0);