ORA-01403: no data found

what is wrong with this code it gives
ORA-01403: no data found
ORA-06512: at line 21

//* Formatted on 3/17/2011 11:21:40 AM (QP5 v5.126.903.23003) */
DECLARE
   CURSOR a_cur
   IS
      SELECT   *
        FROM   myschema.order_tab pc;

   a_rec   a_cur%ROWTYPE;
   f1      DATE;
   f2      DATE;
   r1      DATE;
   r2      DATE;
BEGIN
   OPEN a_cur;

   LOOP
       BEGIN
      FETCH a_cur INTO a_rec;

      EXIT WHEN a_cur%NOTFOUND;

      SELECT   FFS_BASELINE_START_DT_USER,
               FFS_BASELINE_END_DT_USER,
               RX_BASELINE_START_DT_USER,
               RX_BASELINE_END_DT_USER
        INTO   f1,
               f2,
               r1,
               r2
        FROM   myschema_reports.ca_baseline
       WHERE   project_number = a_rec.project_number;

      UPDATE   myschema.order_tab
         SET   FFS_BASELINE_START_DATE = f1,
               FFS_baseline_end_date = f2,
               RX_BASELINE_START_DATE = r1,
               RX_BASELINE_END_DATE = r2
       WHERE   project_number = a_rec.project_number;
    END;
   END LOOP;

   CLOSE a_cur;
END;