добавете изключение като това.
-- Open temporary lob
DBMS_LOB.OPEN(dest_loc, DBMS_LOB.LOB_READWRITE);
begin
-- Load binary file into temporary LOB
DBMS_LOB.LOADFROMFILE(
dest_lob => dest_loc
, src_lob => src_loc
, amount => DBMS_LOB.getLength(src_loc));
exception
when dbms_lob.operation_failed
then
return empty_blob();
end;
..rest of your code.