denyspozniak created an issue (kamailio/kamailio#4314)

### Description

The code below causes Kamailio to crash when sending a simple OPTIONS request. I agree that this is not the most proper way to call the sl function, but it's probably worth paying attention to this issue.

#### Reproduction

```import sys import KSR as KSR

def mod_init(): return kamailio()

class kamailio: def __init__(self): KSR.info('== kamailio init ==\n')

def child_init(self, rank): return 0

def ksr_request_route(self, msg): KSR.x.modf("sl_send_reply", "200", "OK"); return 1 ```

#### Debugging Data

[(gdb) bt full.txt](https://github.com/user-attachments/files/21149798/gdb.bt.full.txt)

[(gdb) info locals.txt](https://github.com/user-attachments/files/21149836/gdb.info.locals.txt)

``` (gdb) list 154 in sl_funcs.c ```

#### Log Messages

``` Program received signal SIGSEGV, Segmentation fault. sl_reply_helper (msg=msg@entry=0x7ffff6fada80, code=200, reason=reason@entry=0x7ffff75d2070 "OK", tag=tag@entry=0x0) at sl_funcs.c:159 159 sl_funcs.c: No such file or directory. ``` ### Additional Information

* **Kamailio Version** - output of `kamailio -v`

``` version: kamailio 6.1.0-dev1 (x86_64/linux) flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, MEM_JOIN_FREE, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLOCKLIST, HAVE_RESOLV_RES, TLS_PTHREAD_MUTEX_SHARED ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_SEND_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: unknown compiled with gcc 9.4.0 ```