plpgsql-fct. fails on NULL in record variables

Hi all,

I'm currently coding some functions in plpgsql for generating
reports out of records in a table. Problem is: NULL values in
records make the complete function fail.
Here is a simple test case (original is more complex with a multi-
table query in the for qres in select... part):

create table test(
id serial,
descr char(4),
data int
);

insert into test (descr, data) values ('set1', 15);
-- record 2 does not have a data value --
insert into test (descr) values ('set2');

create function report(int) returns text as '
declare
    qres record;
    report text;
begin
    for qres in
    select descr, data from test where id=$1
    loop
        report:=qres.descr||'': ''||qres.data;
    end loop;
    return report;
end;'
language 'plpgsql';

now test the function in psql:
test=> select report(1);
  report
----------
 set1: 15
(1 row)

test=> select report(2);
 report
--------

(1 row)

while what I want it to return in the second case is this:
 report
--------
 set2:
(1 row)

'set2: NULL' would be ok as well.

How can I achieve this?

Regards,
Daniel