alexa-app-server: alexa-verifier set the "verify" flag to true and calling from a non echo throws an error

I used the example code here:

var AlexaAppServer = require("alexa-app-server");
var server = new AlexaAppServer( {
	port:3000
    ,verify: true
    ,public_html: "public"
	// Use preRequest to load user data on each request and add it to the request json.
	// In reality, this data would come from a db or files, etc.
	,preRequest: function(json,req,res) {
		//console.log("preRequest fired");
		//json.userDetails = { "name":"Bob Smith" };
	}
	// Add a dummy attribute to the response
	,postRequest: function(json,req,res) {
		//json.dummy = "text";
	}
} );
server.start();

and added the verify flag so that I can pass the skills certification. When I try to make a request through postman it does fail (which is good) but It’s not throwing a 500, instead it throws the following error:

ReferenceError: er is not defined
    at Object.handle (/my/path/node_modules/alexa-app-server/index.js:97:57)
    at next_layer (/my/path/node_modules/alexa-app-server/node_modules/express/lib/router/route.js:103:13)
    at Route.dispatch (/my/path/node_modules/alexa-app-server/node_modules/express/lib/router/route.js:107:5)
    at /my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:195:24
    at Function.proto.process_params (/my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:251:12)
    at next (/my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:189:19)
    at Layer.handle (/my/path/node_modules/alexa-app-server/index.js:79:15)
    at trim_prefix (/my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:226:17)
    at /my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:198:9
    at Function.proto.process_params (/my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:251:12)
    at next (/my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:189:19)
    at next (/my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:166:38)
    at Layer.staticMiddleware [as handle] (/my/path/node_modules/alexa-app-server/node_modules/serve-static/index.js:55:61)
    at trim_prefix (/my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:226:17)
    at /my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:198:9
    at Function.proto.process_params (/my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:251:12)
    at next (/my/path/node_modules/alexa-app-server/node_modules/express/lib/router/index.js:189:19)
    at IncomingMessage.<anonymous> (/my/path/node_modules/alexa-app-server/index.js:184:5)
    at emitNone (events.js:86:13)
    at IncomingMessage.emit (events.js:185:7)
    at endReadableNT (_stream_readable.js:974:12)
    at _combinedTickCallback (internal/process/next_tick.js:74:11)
    at process._tickCallback (internal/process/next_tick.js:98:9)