function em_booking_summary_approved_link($booking_actions, $EM_Booking){
    $url = $EM_Booking->get_event()->get_bookings_url();
	$s = absint($EM_Booking->booking_status);
    if ( $s == 0 ){
		$booking_actions['approve'] = '<a class="em-bookings-approve em-bookings-approve-'. $s .'" href="'.em_add_get_params($url, array('action'=>'bookings_approve', 'booking_id'=>$EM_Booking->booking_id)).'">'.__('Approve','events-manager').'</a>';
    }
	return $booking_actions;
}
add_filter('em_bookings_table_cols_col_action','em_booking_summary_approved_link',10,2);