Fix segfault on registrations when we are not challenged for aut. can't match…

Fix segfault on registrations when we are not challenged for aut.  can't match scheme and realm if there isn't one.

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@3282 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/endpoints/mod_sofia/mod_sofia.c

@@ -4090,7 +4090,7 @@ static void sip_r_register(int status,
 		} else if (profile) {
 			outbound_reg_t *oregp;
 			for (oregp = profile->registrations; oregp; oregp = oregp->next) {
-				if (!strcasecmp(oregp->register_scheme, scheme) && !strcasecmp(oregp->register_realm, realm)) {
+				if (scheme && realm && !strcasecmp(oregp->register_scheme, scheme) && !strcasecmp(oregp->register_realm, realm)) {
 					oreg = oregp;
 					break;
 				}