Game closes when mobile back button is pressed from webview

cocos2d-x JavaScript
#1

following is the webview.
showHelpPage: function () {
‘use strict’;

    var size = app.dmm.size,
      scheme = "mqkey";

    this.webview = new ccui.WebView("res/faq/faq-template/index.html"),
    this.webview.setContentSize(size.width, size.height);
    this.webview.setPosition(size.width * 0.5, size.height * 0.5);
    this.webview.setScalesPageToFit(true);
    this.webview.setJavascriptInterfaceScheme(scheme);
    try{
    this.webview.setOnJSCallback(this.jsCallback);
    }catch(e){
    cc.log("Yep "+e);
   }
    this.addChild(this.webview);
   },

Please help…