Private Messages For WordPress: Non-Admin PM to admin ONLY

// Get all users of blog
                    if (current_user_can('manage_options')):
                        ## Original Code:
                        //$users = $wpdb->get_results( "SELECT * FROM $wpdb->users ORDER BY display_name ASC" );
                        $users = get_users('orderby=nicename');
                    else:
                        $users = get_users('orderby=nicename&role=administrator');
                    endif;




                    if ( $option['type'] == 'autosuggest' )
                    { // if auto suggest feature is turned on
                        ?>
                        <input id="recipient" type="text" name="recipient" class="large-text" />
                        <?php

                    }
                    else
                    { // classic way: select recipient from dropdown list
                        ?>
                        <select name="recipient[]" multiple="multiple" size="5">
                            <?php
                            foreach ( $users as $user )
                            {
                                $selected = ( $user->user_nicename == $recipient ) ? ' selected="selected"' : '';
                                echo "<option value='$user->user_nicename'$selected>$user->user_nicename</option>";
                            }
                            ?>
                        </select>
                        <?php
                    }