Oracle XML:Ignorar Não Existe Nó

CREATE TABLE my_test
     (
          LastName varchar2(20),
          phone   NUMBER,
          code    varchar2(20),
          address VARCHAR2(100)
     );

SET serveroutput ON
DECLARE
l_xml xmltype;
l_val VARCHAR2(1000) := '<begin>
    <entry>
        <lastname>gordon</lastname>
        <numberlist>
            <number>100</number>
            <codelist>
                 <code>213</code>
            </codelist>
        </numberlist>
        <address>
            <addresslist>jl. jalan pelan-pelan ke bekasi, indonesia</addresslist>
        </address>
    </entry>
    <entry>
        <lastname>mark</lastname>
        <address>
            <addresslist>jl. jalan cepet-cepet ke jakarta, indonesia</addresslist>
        </address>
    </entry>
</begin>';
     l_lastname varchar2(50);
     l_phone number;
     l_code number;
     l_address  varchar2(200);
BEGIN
     l_xml        := xmltype(l_val);

     FOR x IN
     (SELECT VALUE(p) col_val
     FROM TABLE(XMLSEQUENCE(EXTRACT(l_xml, '/begin/entry'))) p
     )
     loop

IF x.col_val.existsnode('/entry/lastname/text()') > 0 THEN
         l_lastname := x.col_val.extract('/entry/lastname/text()').getstringval();
END IF;
if x.col_val.existsnode('/entry/numberlist/number/text()') > 0 then
     l_phone := x.col_val.extract('/entry/numberlist/number/text()').getstringval();
end if;
if x.col_val.existsnode('/entry/numberlist/codelist/code/text()') > 0 then
     l_code := x.col_val.extract('/entry/numberlist/codelist/code/text()').getstringval();
end if;
IF x.col_val.existsnode('/entry/address/addresslist/text()') > 0 THEN
         l_address := x.col_val.extract('/entry/address/addresslist/text()').getstringval();
end if;
INSERT INTO my_test
     (
          lastname,
          phone,
          code,
          address
     )
     VALUES
     (
          l_lastname,
          l_phone,
          l_code,
          l_address
     );
     l_lastname := null;
     l_phone := null;
     l_code := null;
     l_address := null;
     end loop;
commit;
end;