prevent searchword redirect when we're serving an endpoint request

see https://github.com/GigaOM/legacy-pro/issues/4101
do not enable searchword redirect when in admin dashboard

see https://github.com/GigaOM/legacy-pro/issues/4107
correctly check the emptiness of the result of scriblio()->get_terms_as_facets()
Merge pull request #51 from wluo/github-4101

prevent searchword redirect when we're serving an endpoint request or in admin dashboard