I am getting this error while running my gattling code [at io.gatling.http.protocol.HttpProtocol$.apply(HttpProtocol.scala:71)]

import io.gatling.core.Predef._

import io.gatling.http.Predef._

import scala.concurrent.duration._

class Simulations extends Simulation {

def test(){

val httpConf = http

.baseURL(“http://computer-database.gatling.io”)

.acceptHeader(“text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8”)

.doNotTrackHeader(“1”)

.acceptLanguageHeader(“en-US,en;q=0.5”)

.acceptEncodingHeader(“gzip, deflate”)

.userAgentHeader(“Mozilla/5.0 (Windows NT 5.1; rv:31.0) Gecko/20100101 Firefox/31.0”)

val scn = scenario(“BasicSimulation”)

.exec(http(“request_1”)

.get("/"))

.pause(5)

setUp(

scn.inject(atOnceUsers(1)).protocols(httpConf))

}}

object Demo {

def main(args: Array[String]) {

val pt = new Simulations

pt.test()

}

}