Insert null value - sql

Question

I'm trying to Insert a double precision (ilosc_zlec) value into a table (M_ZAMWLASNEPOZ). First I use a select statement to get the value. After I run this part of code, I can see the correct value in the variable ( 39 ). Next I'm trying to insert the selected values in the table and most of them get inserted but field ILOSC with should become the value of ilosc_zlec shows NULL. Both ILOSC, ilosc_zlec are double precision variables.
for select t.strumet_katzw,a.kategoria,a.rok_zam,a.symbol_zam,a.indeks,a.nazwa,a.wyroznik,a.ilosc_zlec,a.lp_zam from m_zlecenia a
left join m_przewod_gl g
on g.kat_zlec= a.kategoria and g.rok_zlec= a.rok_zam and g.symb_zlec= a.symbol_zam and g.lp_zlec= a.lp_zam
left join m_przewod_op p
on p.kat_zlec= a.kategoria and p.rok_zlec= a.rok_zam and p.symb_zlec= a.symbol_zam and p.lp_zlec= a.lp_zam and p.nr_przew=g.nr_poz
left join m_kot t
on t.kod_oper= p.kod_oper
where a.wyroznik=:wyroznik and a.grupa_zl= 'KOP' and a.data_wykon is null and f_mid(p.kod_oper,1,4)='KOOD' and t.strumet_katzw is not null
into: strumet_katzw,:kategoria, :rok_zam, :symbol_zam, :indeks, :nazwa, :wyroznik, :ilosc_zlec,:lp_zam
do begin
select symbol_zam from m_zamwlasne where kategoria=:strumet_katzw and F_MID(symbol_zam,1,8) = (:symbol_zam||f_mid(:indeks,5,3)) into: symb_szukan_nagl ;
-- wypelniasz pozycje naglowka
INSERT INTO M_ZAMWLASNEPOZ (KATEGORIA, ROK_ZAM, SYMBOL_ZAM, LP_ZAM, INDEKS, ILOSC, TERMIN, CENA_ZAM, POBRANO_IL, ZREALIZOWANO, DATA_ZM, OPER, KOD_KONTRO, ZAKUP_DLA, NA_PRZEWOD, IL_PO_KONTROLI, JM, ILOSC_ZAK, REL_JM_ZAK, NR_ZAPOTRZEB, DATA_POTW, OPIS_POZ2, OPIS_POZ, KOOP_WYROB, KOOP_WYROB_ILOSC, POBRANO_KOOP, SKAD_KOPIA, TYP_INDEKSU, SUMA_DOST, DATA_REALIZ, LP_OFERTY, KONTO_KOSZT, NA_NADRZ, PRZEDMIOT, RABAT, PR_RABAT, CENA_JEDN, LP_OPER, ILOSC_REJOP_KOOP, ROZLICZONE)
VALUES (:strumet_katzw, :rok_zam, :symb_szukan_nagl, :lp_zam, :indeks, :ilosc_zlec, 'now', 0, 0, 'T', 'now', user, 'NN', NULL, NULL, 0, 'SZT', 0, 0, NULL, 'NOW', NULL, NULL, NULL, 0, 0, NULL, 'I', 0, 'NOW', 1, NULL, NULL, 'a', 0, 0, 0, NULL, NULL, NULL);
suspend;
end