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### Description

I get SIGSEGV in the start-up time with the wrong kamailio config. To get a backtrace, I set up gdb: ``` gdb --args /home/devel/build_dir/build/sbin/kamailio -m 8 -n 1 -w . -f /tmp/kamailio.cfg (gdb) start (gdb) c ``` Then I see the error and the gdb output (attached below).

### Troubleshooting

#### Reproduction

Pass to `ds_select_domain` non-constant value, e.g. ``` $avp(num) = 13; if (!ds_select_domain( 101, 4, $avp(num) )) { return 1; } ```

#### Debugging Data

``` Program received signal SIGSEGV, Segmentation fault. 0x00000000006a1daf in rve_destroy (rve=0x6f6c5f7265766f6c) at core/rvalue.c:147 147 if (rve->op==RVE_RVAL_OP){ Missing separate debuginfos, use: debuginfo-install audit-libs-2.8.5-4.el7.x86_64 bzip2-libs-1.0.6-13.el7.x86_64 elfutils-libelf-0.176-4.el7.x86_64 keyutils-libs-1.5.8-3.el7.x86_64 krb5-libs-1.15.1-46.el7.x86_64 libacl-2.2.51-15.el7.x86_64 libattr-2.4.46-13.el7.x86_64 libcap-2.22-11.el7.x86_64 libcap-ng-0.7.5-4.el7.x86_64 libcom_err-1.42.9-17.el7.x86_64 libdb-5.3.21-25.el7.x86_64 libgcc-4.8.5-39.el7.x86_64 libselinux-2.5-15.el7.x86_64 libstdc++-4.8.5-39.el7.x86_64 lm_sensors-libs-3.4.0-8.20160601gitf9185e5.el7.x86_64 lua-5.1.4-15.el7.x86_64 net-snmp-agent-libs-5.7.2-48.el7_8.1.x86_64 net-snmp-libs-5.7.2-48.el7_8.1.x86_64 nspr-4.21.0-1.el7.x86_64 nss-3.44.0-7.el7_7.x86_64 nss-softokn-freebl-3.44.0-8.el7_7.x86_64 nss-util-3.44.0-4.el7_7.x86_64 openssl-libs-1.0.2k-19.el7.x86_64 pcre-8.32-17.el7.x86_64 perl-libs-5.16.3-295.el7.x86_64 popt-1.13-16.el7.x86_64 rpm-libs-4.11.3-43.el7.x86_64 tcp_wrappers-libs-7.6-77.el7.x86_64 xz-libs-5.2.2-1.el7.x86_64 zlib-1.2.7-18.el7.x86_64 (gdb) bt #0 0x00000000006a1daf in rve_destroy (rve=0x6f6c5f7265766f6c) at core/rvalue.c:147 #1 0x00000000006a266e in rve_destroy (rve=0x7ffff6c77f08) at core/rvalue.c:168 #2 0x00000000007d2884 in free_mod_func_action (a=0x7ffff6c76658) at core/cfg.y:4047 #3 0x00000000007ce97f in yyparse () at core/cfg.y:3459 #4 0x000000000042f396 in main (argc=9, argv=0x7fffffffe448) at main.c:2320 (gdb) p rve $1 = (struct rval_expr *) 0x6f6c5f7265766f6c (gdb) p rve->op Cannot access memory at address 0x6f6c5f7265766f6c (gdb) ```

#### Log Messages

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``` 0(425) CRITICAL: <core> [core/cfg.y:3589]: yyerror_at(): parse error in config file /tmp/kamailio.cfg, line 653, column 58-66: function ds_select_domain: parameter 3 is not constant ```

### Possible Solutions

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### Additional Information

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

``` version: kamailio 5.4.3 (x86_64/linux) 430602 flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, 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_BLACKLIST, HAVE_RESOLV_RES ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_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: 430602 compiled on 17:40:07 Jan 29 2021 with gcc 4.8.5 ```

* **Operating System**:

<!-- Details about the operating system, the type: Linux (e.g.,: Debian 8.4, Ubuntu 16.04, CentOS 7.1, ...), MacOS, xBSD, Solaris, ...; Kernel details (output of `uname -a`) -->

``` (paste your output here) ```