### Description

IMS reregistration triggers core dump on 5.1.4.

1) Create IMS registration 2) Put IMS terminal offline 3) Put it back online to update IMS registration 4) Register requests time out on s-cscf

### Troubleshooting

This seems to be related to the cleaning up contacts during registration/re-registration. Related to the https://github.com/kamailio/kamailio/pull/1562. This PR did not make it to 5.1.4 but affected code was clearly involved according to the logs.

#### Reproduction

#### Debugging Data

#### Log Messages

``` Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [impurecord.c:451]: process_impurecord(): There are 2 contacts to expire/unlink Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [impurecord.c:454]: process_impurecord(): expiring contact 0: [sip:XXXYY4000013362@10.110.1 Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [impurecord.c:1237]: unlink_contact_from_impu(): asked to unlink contact [0x7f7141cf29a0] => [sip:XXXYY4000 Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [impurecord.c:1106]: remove_impucontact_from_list(): deleting mid list Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [usrloc_db.c:1130]: db_unlink_contact_from_impu(): DB: un-linking contact to IMPU Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: <core> [db_res.c:120]: db_new_result(): allocate 56 bytes for result set at 0x7f714ba6e620 Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: <core> [db_res.c:79]: db_free_columns(): freeing 0 columns Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: <core> [db_res.c:138]: db_free_result(): freeing result set at 0x7f714ba6e620 Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [usrloc_db.c:1155]: db_unlink_contact_from_impu(): Delete query success Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [udomain.c:852]: unref_contact_unsafe(): decrementing ref count on contact [sip:XXXYY4000013362@10.110.1.69 Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [udomain.c:855]: unref_contact_unsafe(): contact [sip:XXXYY4000013362@10.110.1.69:5060;alias=10.110.1.69~50 Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [impurecord.c:1263]: unlink_contact_from_impu(): unlinking contact [0x7f7141cf29a0] => [sip:XXXYY4000013362 Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [impurecord.c:454]: process_impurecord(): expiring contact 1: [sip:XXXYY4000013362@10.110.1 Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [impurecord.c:1237]: unlink_contact_from_impu(): asked to unlink contact [0x7f7141cfc878] => [sip:XXXYY4000 Jul 24 07:21:00 scscf scscfXXXYYY-ecs[798]: 1(6) DEBUG: ims_usrloc_scscf [impurecord.c:1103]: remove_impucontact_from_list(): **deleting tail**

Jul 24 07:22:21 scscf scscfXXXYYY-ecs[798]: 15(20) DEBUG: ims_registrar_scscf [save.c:840]: update_contacts(): updating contacts in RE-REGISTRATION state Jul 24 07:22:21 scscf scscfXXXYYY-ecs[798]: 15(20) DEBUG: ims_registrar_scscf [save.c:519]: update_contacts_helper(): updating the contacts for IMPU <sip:XXXYY4000013362@ims.mnc006. Jul 24 07:22:21 scscf scscfXXXYYY-ecs[798]: 15(20) DEBUG: <core> [ims_getters.c:812]: cscf_get_sos_uri_param(): cscf_get_sos_uri_param: searching through the uri parameters:alias=10 Jul 24 07:22:21 scscf scscfXXXYYY-ecs[798]: 15(20) DEBUG: <core> [ims_getters.c:823]: cscf_get_sos_uri_param(): cscf_get_sos_uri_param:name: alias body: 10.110.1.71~5060~1 Jul 24 07:22:21 scscf scscfXXXYYY-ecs[798]: 15(20) DEBUG: ims_registrar_scscf [save.c:137]: calc_contact_expires(): Calculated expires for contact is 600000 Jul 24 07:22:21 scscf scscfXXXYYY-ecs[798]: 15(20) DEBUG: ims_registrar_scscf [save.c:548]: update_contacts_helper(): Need to update contact: <sip:XXXYY4000013362@10.110.1.71:5060;a Jul 24 07:22:21 scscf scscfXXXYYY-ecs[798]: 15(20) DEBUG: ims_registrar_scscf [save.c:550]: update_contacts_helper(): packing contact information Jul 24 07:22:21 scscf scscfXXXYYY-ecs[798]: 15(20) DEBUG: ims_registrar_scscf [save.c:556]: update_contacts_helper(): adding/updating contact based on prior existence Jul 24 07:22:21 scscf scscfXXXYYY-ecs[798]: 15(20) DEBUG: ims_usrloc_scscf [impurecord.c:748]: get_scontact(): looking for contact [sip:XXXYY8000099992@10.110.1.71:5060;alias=10.110 Jul 24 07:22:21 scscf scscfXXXYYY-ecs[798]: 15(20) DEBUG: ims_registrar_scscf [save.c:562]: update_contacts_helper(): inserting new contact Jul 24 07:22:21 scscf scscfXXXYYY-ecs[798]: 15(20) DEBUG: ims_usrloc_scscf [impurecord.c:562]: insert_scontact(): INSERTing ucontact in usrloc module Jul 24 07:22:21 scscf kernel: traps: kamailio[7186] general protection ip:7f7146511000 sp:7ffc9f3719a0 error:0 in ims_usrloc_scscf.so[7f71464e7000+8f000]

```

#### SIP Traffic


``` (paste your sip traffic here) ```

### Possible Solutions

### Additional Information

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

``` version: kamailio 5.1.4 (x86_64/linux) ```

* **Operating System**:

``` Linux scscf 4.14.48-coreos-r2 #1 SMP Thu Jun 14 08:23:03 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux ```