Simply return null if no response received instead of crashing

src/mdns.zig

@@ -115,7 +115,7 @@ fn receive_response(sock: socket, ip_info: util.IPInfo) !util.IP {
     const n: usize = blk: {
         const ret = std.c.recv(sock, &buff, MSG_BUFF_SIZE, 0);
         if (ret < 0) {
-            return MDNSError.UDPRecvFail;
+            return util.IP{}; // no reply means no matching record on network
         } else {
             break :blk @bitCast(ret);
         }