APEX

Dear Expert,

Currently i'm using oracle apex 3.0.1.
I'm having a problem on displaying blob content (from database table) as pdf file on oracle application express but i'm able to save to download the pdf.
Below is the procedure that i used to display blob content,

PROCEDURE lf_html_pdf (pv_image IN VARCHAR2, pv_index IN NUMBER) is
l_mime VARCHAR2 (255);
l_length NUMBER;
l_file_name VARCHAR2 (2000);
lob_loc BLOB;

BEGIN
begin
selecT OI_BLOB,DBMS_LOB.getlength (OI_BLOB)
into lob_loc,l_length
from ord_img
where oi_tno= pv_image
and oi_ti='PDF'
and oi_idx=pv_index;
exception
when others then
null;
end;

OWA_UTIL.mime_header (NVL (l_mime, 'application/pdf'), FALSE);
HTP.p ('Content-length: ' || l_length);
OWA_UTIL.http_header_close;
WPG_DOCLOAD.download_file (lob_loc);
END lf_html_pdf;


I get the error message as below when i execute the procedure above;
Error report:
ORA-06502: PL/SQL: numeric or value error
ORA-06512: at "SYS.OWA_UTIL", line 356
ORA-06512: at "SYS.OWA_UTIL", line 415
ORA-06512: at "HCLABPRO.PKG_PDF", line 220
ORA-06512: at line 2
*06502. 00000 - "PL/SQL: numeric or value error%s"*

I'm appreciated if expert can have me on the problem above?

Thanks
From junior