allow empty string in query

dns.packer.js

@@ -29,7 +29,7 @@ var dnspack = exports.DNS_PACKER = {
     dv.setUint16(10, (packet.additional||[]).length + (packet.payload ? 1 : 0), false);
 
     function lint(r) {
-      if (!r.name) {
+      if (!r.name && 'string' !== typeof r.name) {
         throw new Error("missing name");
       }
 
@@ -70,7 +70,8 @@ var dnspack = exports.DNS_PACKER = {
         labelsMap[total] = { total: total, name: sequence };
         labelsMap[sequence] = labelsMap[total];
       }
-      sequence.split('.').forEach(function (label) {
+      // allow 0-length string for TLD root NS queries
+      (sequence && sequence.split('.') || []).forEach(function (label) {
         dv.setUint8(total, label.length, false);
         total += 1;