'Handle when the app is not in the app map (as result of filtering).'

def test_no_exist(self):

    app = mkt.site.tests.app_factory()
    field = AppESField()
    field.context = {'app_map': {}, 'request': mkt.site.tests.req_factory_factory('')}
    data = field.to_representation(app.id)
    ok_((not data))
