FID get null (2)

Dear List i check from log get this

GET
/push?&uid=abc&pwd=pwd&serviceid=12345&transid=(null)&smstype=0&msisdn=62858805&sms=test


Content-Length:
118..Content-Type: text/xml....<?xml
version='1.0'?><PUSH><STATUS>0</STATUS><TRANSID>(null)</TRANSID><MSG>Messagge
success</MSG>

thats why operator reaction with null , how to make the transid become like
this?
GET
/push?&uid=abc&pwd=pwd&serviceid=12345&transid=&smstype=0&msisdn=62858805&sms=test

only if there is no foreign id


this is snip of our scripts (it work for MO but not via sendsms / push
system coz not need trx-id for push

 /* Get trx-id */
    if (octstr_search(url, octstr_create("transid="), 0) == -1) {
        octstr_format_append(url, "&transid=%S", sms->sms.foreign_id);
    }


Regards