made uacomment optional

install/generator-cyphernode/generators/app/index.js

@@ -139,6 +139,15 @@ module.exports = class extends Generator {
     return this.props && this.props[name];
   }
 
+  _optional(input,validator) {
+    if( input === undefined || 
+        input === null || 
+        input === '' ) {
+      return true;
+    }
+    return validator(input);
+  }
+
   _ipOrFQDNValidator( host ) {
     host = (host+"").trim();
     if( !(validator.isIP(host) || 

install/generator-cyphernode/generators/app/prompters/100_bitcoin.js

@@ -77,7 +77,7 @@ module.exports = {
       default: utils._getDefault( 'bitcoin_uacomment' ),
       message: prefix()+'Any UA comment?'+'\n',
       filter: utils._trimFilter,
-      validate: utils._UACommentValidator
+      validate: (input)=> {return utils._optional(input,utils._UACommentValidator) }
     }];
   },
   env: function( props ) {