excludeIf should work with @Content too

ExcludeIf affects only on links. In some cases we need omit embedded relations too.
For example:

   *@Rest\Relation("http://hautelook.com/rels/invitations/reminders",
   *     embed = @Rest\Content(property = ".childs"),
   *     excludeIf = {".showChilds" = null}
   * )