Don't attempt to make use of the dynamic_exclude_static ACL if DNS lookup fails.

(closes issue ASTERISK-18321)
Reported by Dan Lukes
Patches:
	ASTERISK-18321.patch by Mark Michelson (license #5049)



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@364341 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -27802,7 +27802,7 @@ static struct sip_peer *build_peer(const char *name, struct ast_variable *v, str
 
 		ast_string_field_set(peer, tohost, srvlookup);
 
-		if (global_dynamic_exclude_static) {
+		if (global_dynamic_exclude_static && !ast_sockaddr_isnull(&peer->addr)) {
 			int ha_error = 0;
 			sip_cfg.contact_ha = ast_append_ha("deny", ast_sockaddr_stringify_addr(&peer->addr), 
 							sip_cfg.contact_ha, &ha_error);