res_pjsip: Check return from pjsip_parse_uri calls

Updated ast_sip_create_rdata_with_contact and registrar_find_contact
to check the return from pjsip_parse_uri before attempting to
use the uri returned.

ASTERISK-28402
Reported-by: Ross Beer

Change-Id: I9810b3b163c45ed5a56ec743586e5ce107f13ba7