### Description
I tried to configure the carrierroute module with the description loaded from
the database into an avp. But it crashes with a segfault while startup.
### Troubleshooting
Reproduction
```
/* - carrierroute params --- */
modparam("carrierroute", "config_source", "db")
modparam("carrierroute", "db_url", )
modparam("carrierroute", "fetch_rows", 2000)
modparam("carrierroute", "db_load_description", 1)
modparam("carrierroute", "match_mode", 10)
modparam("carrierroute", "avoid_failed_destinations", 1)
```
```
if (cr_route("default", "default", "$(rU{s.strip,1})", "$rU", "call_id",
"destination")) {
}
```
Debugging Data
```
#0 avp_name_fixup (param=0x8018d1330) at cr_fixup.c:187
187 if (((gparam_p)(*param))->v.pve->spec->type == PVT_AVP &&
[New Thread 80165a600 (LWP 100186/)]
(gdb) bt full
#0 avp_name_fixup (param=0x8018d1330) at cr_fixup.c:187
No locals.
#1 0x0008072f0256 in cr_route_fixup (param=0x8018d1330, param_no=6) at
cr_fixup.c:242
my_hash_source = shs_call_id
#2 0x0073238e in fix_actions (a=0x8018d1258) at core/route.c:919
t = (struct action *) 0x8018d1258
p = (struct proxy_l *) 0x0048
tmp = 0x0
tmp_p = (void *) 0x8018d1660
ret = 0
i = 5
cmd = (sr31_cmd_export_t *) 0x80186dcd0
s = {s = 0x ,
len = 0}
he = (struct hostent *) 0x4
ip = {af = 4859304, len = 0, u = {addrl = 0x7fff9be0, addr32 =
0x7fff9be0, addr16 = 0x7fff9be0, addr = 0x7fff9be0 "?"}}
si = (struct socket_info *) 0x7fff9c10
lval = (struct lvalue *) 0x0001
rve = (struct rval_expr *) 0x0
err_rve = (struct rval_expr *) 0x1
rve_type = RV_NONE
err_type = 48625432
expected_type = RV_NONE
rv = (struct rvalue *) 0x9b6cf7
rve_param_no = 0
#3 0x0068a1c4 in fix_rval (rv=0x8018d36c8, rve=0x8018d36c0) at
core/rvalue.c:2873
No locals.
#4 0x0068843e in fix_rval_expr (p=0x8018d36c0) at core/rvalue.c:3797
rve = (struct rval_expr *) 0x8018d36c0
ret = 32767
#5 0x0072aa08 in fix_actions (a=0x8018c94d0) at core/route.c:706
t = (struct action *) 0x8018d1d18
p = (struct proxy_l *) 0x68341cdd25
tmp = 0x3
tmp_p = (void *) 0x8018cc9c0
ret = 0
i = 1
cmd = (sr31_cmd_export_t *) 0x801869de0
s = {s = 0x8018cc9c0 "", len = 5}
he = (struct hostent *) 0x9b6cf7
ip = {af = 6302080, len = 0, u = {addrl = 0x7fffcfc0, addr32 =
0x7fffcfc0, addr16 = 0x7fffcfc0, addr = 0x7fffcfc0 ""}}
si = (struct socket_info *) 0x7fffd0a0
lval = (struct lvalue *) 0x800f42023
rve = (struct rval_expr *) 0x8018d36c0
err_rve = (struct rval_expr *) 0x0
rve_type = RV_INT
err_type = 9938251
expected_type = 32767
rv = (struct rvalue *) 0x8018ccf20
rve_param_no = 0
#6 0x0073fd6d in fix_rl (rt=0xce3830) at core/route.c:2088
i = 0
ret = -12096
#7 0x0073fc37 in fix_rls () at core/route.c:2104
ret = 4
#8 0x0043b0ae in main (argc=4, argv=0x7fffeb30) at main.c:2635
cfg_stream = (FILE *) 0x8011fdc90
c = -1
r = 1
tmp = 0x800f84aa2 "H\213\vH;M?u\aH\203?([]??\225!??f\017\037\204"
tmp_len = 32767
port = -5424
proto = 0
options = 0x979297
":f:cm:M:dVIhEeb:l:L:n:vKrRDTN:W:w:t:u:g:P:G:SQ:O:a:A:x:X:Y:"
ret = -1
seed = 2763663412
rfd = 4
debug_save = 3
debug_flag = 1
dont_fork_cnt = 1
n_lst = (struct name_lst *) 0x7fffeaa0
p = 0x4
st = {st_dev = 93, st_ino = 160517, st_mode = 16832, st_nlink = 2,
st_uid = 986, st_gid = 986, st_rdev = 332063, st_atim = {tv_sec = 1459764184,
tv_nsec = 513386000},
st_mtim = {tv_sec = 1502352532, tv_nsec = 990638000}, st_ctim = {tv_sec =
1502352532, tv_nsec = 990638000}, st_size = 512, st_blocks = 8, st_blksize =
32768, st_flags = 0,
st_gen = 3958570559, st_lspare = 0, st_birthtim = {tv_sec = 1459764184,
tv_nsec = 513356000}}
Current language: auto; currently minimal
```
Log Messages
```
0(45720) DEBUG: [core/route.c:872]: fix_actions(): fixing cr_route()
0(45720) DEBUG: [core/pvapi.c:419]: pv_spec_lookup(): PV
<$(rU{s.strip,1})> is not in cache
0(45720) DEBUG: [core/pvapi.c:293]: pv_cache_add(): pvar
[$(rU{s.strip,1})] added in cache
0(45720) DEBUG: [core/pvapi.c:321]: pv_cache_lookup(): pvar [$rU] found
in cache
Segmentation fault (core dumped)
```
SIP Traffic
```
none
```
### Possible Solutions
### Additional Information
* **Kamailio Version** - output of `kamailio -v`
```
# kamailio -v
version: kamailio 5.1.0-dev5 (x86_64/freebsd)
flags: STATS: Off, USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS,
