user id to dropdown

I have been using this function to change the user id to a dropdown with editing permission up to contributor and now it doesn't seem to be working. Any ideas?

add_filter('frm_setup_new_fields_vars', 'show_user_dropdown', 15, 2);
add_filter('frm_setup_edit_fields_vars', 'show_user_dropdown', 15, 3);
function show_user_dropdown($values, $field, $entry_id=false){
if ( $values['type'] == 'user_id' && !is_admin() && current_user_can('contributor') ){
$values['type'] = 'select';
$values['autocom'] = 1;// make it autocomplete
$values['options'] = FrmProFieldsHelper::get_user_options();
$values['use_key'] = true;
$values['custom_html'] = FrmFieldsHelper::get_default_html('select');
}
return $values;
}