Assigning null to an array element in plpgsql

Hi all,

I believe this is a bug. The following function returns 'foo' instead
of null:
---------------
create or replace function test() returns varchar as '
declare
    s    varchar[] := ''{}'';
begin
    s[1] := ''foo'';
    s[1] := null;

    return s[1];
end;
' language 'plpgsql';
----------------

If s is not initialized to an empty set in the declaration, the
function works as expected. I'm running 7.4.9 on FreeBSD 5.4.

Gene