domain add: Try fallback if the list of name servers is empty (#111)

lib/index.js

@@ -354,7 +354,7 @@ export default class Now extends EventEmitter {
         if (this._debug) console.timeEnd(`> [debug] #${attempt} GET /whois-ns${fallback ? '-fallback' : ''}`);
         const body = await res.json();
         if (200 === res.status) {
-          if (!body.nameservers && !fallback) {
+          if ((!body.nameservers || body.nameservers.length === 0) && !fallback) {
             // if the nameservers are `null` it's likely
             // that our whois service failed to parse it
             return this.getNameservers(domain, { fallback: true });