Resolve some crashes/exceptions observed today when used by ircd.js

ircd.js kept crashing on startup on vert with these errors, right after it
logged:
Accepting new connection on port 6667
0832 Accepted new connection: 71.95.196.36 port 55646
[UNREG] Resolving IP: 71.95.196.36

exec/load/dns.js

@@ -211,10 +211,14 @@ DNS.prototype.handle_response = function(sock) {
 	var tmp;
 
 	function string_to_int16(str) {
+		if(!str)
+			return 0;
 		return ((ascii(str[0])<<8) | (ascii(str[1])));
 	}
 
 	function string_to_int32(str) {
+		if(!str)
+			return 0;
 		return ((ascii(str[0])<<24) | (ascii(str[1]) << 16) | (ascii(str[1]) << 8) | (ascii(str[1])));
 	}
 
@@ -393,6 +397,8 @@ DNS.prototype.handle_response = function(sock) {
 	delete this.outstanding[id];
 
 	ret.id = id;
+	if(!resp)
+		return null;
 	ret.response = !!(ascii(resp[2]) & 0x80);
 	if (!ret.response)
 		return null;