Cannot read property 'length' of undefined jade

I am new to nodejs and learning it by building one small project(Blog), facing below mentioned issue while submitting add post form details. I have also added code for addPost.jade and post.js.

TypeError: E:\Web projects\NodeJs projects\nodeBlog\views\addpost.jade:19
  17|               label Category:
  18|               select.form-control(name='category')
> 19|                   each cat, i in catList
  20|                       option(value = '#{cat.title}') #{cat.title}
  21|           .form-group
  22|               label Body:

Cannot read property 'length' of undefined
    at eval (eval at <anonymous> (E:\Web projects\NodeJs projects\nodeBlog\node_modules\jade\lib\index.js:218:8), <anonymous>:210:31)
    at eval (eval at <anonymous> (E:\Web projects\NodeJs projects\nodeBlog\node_modules\jade\lib\index.js:218:8), <anonymous>:247:4)
    at eval (eval at <anonymous> (E:\Web projects\NodeJs projects\nodeBlog\node_modules\jade\lib\index.js:218:8), <anonymous>:383:22)
    at res (E:\Web projects\NodeJs projects\nodeBlog\node_modules\jade\lib\index.js:219:38)
    at Object.exports.renderFile (E:\Web projects\NodeJs projects\nodeBlog\node_modules\jade\lib\index.js:380:38)
    at Object.exports.renderFile (E:\Web projects\NodeJs projects\nodeBlog\node_modules\jade\lib\index.js:370:21)
    at View.exports.__express [as engine] (E:\Web projects\NodeJs projects\nodeBlog\node_modules\jade\lib\index.js:417:11)
    at View.render (E:\Web projects\NodeJs projects\nodeBlog\node_modules\express\lib\view.js:126:8)
    at tryRender (E:\Web projects\NodeJs projects\nodeBlog\node_modules\express\lib\application.js:639:10)
    at EventEmitter.render (E:\Web projects\NodeJs projects\nodeBlog\node_modules\express\lib\application.js:591:3)
    at ServerResponse.render (E:\Web projects\NodeJs projects\nodeBlog\node_modules\express\lib\response.js:960:7)
    at E:\Web projects\NodeJs projects\nodeBlog\routes\post.js:89:6
    at Layer.handle [as handle_request] (E:\Web projects\NodeJs projects\nodeBlog\node_modules\express\lib\router\layer.js:95:5)
    at next (E:\Web projects\NodeJs projects\nodeBlog\node_modules\express\lib\router\route.js:131:13)
    at Immediate.<anonymous> (E:\Web projects\NodeJs projects\nodeBlog\node_modules\multer\lib\make-middleware.js:53:37)
    at runCallback (timers.js:655:20)

addPost.jade file which gets rendered fine for GET request

//Created by Sinner on 11-Apr-17.

extends layout

block content
    h1=title
    ul.errors
        if errors
            each error, i in errors
                li.alert.alert-danger #{error.msg}

        form(method='post', action='/posts/add', enctype='multipart/form-data')
            .form-group
                label Title:
                input.form-control(name='title', type='text')
            .form-group
                label Category:
                select.form-control(name='category')
                    each cat, i in catList
                        option(value = '#{cat.title}') #{cat.title}
            .form-group
                label Body:
                textarea.form-control(name='body', id='body')
            .form-group
                label Main Image:
                input.form-control(name='mainimage', type='file')
            .form-group
                label Author:
                select.form-control(name='author')
                    option(value='Akshay Gupta') Akshay Gupta
                    option(value='Riddhi Tandon') Riddhi Tandon
            input.btn.btn-default(name='Submit', type='submit', value='Save')
            script(src='/ckeditor/ckeditor.js')
            script CKEDITOR.replace('body')

post.js file

var express = require('express');
var router = express.Router();
var mongo = require('mongodb');
var db = require('monk')('localhost/nodeblog');
var multer = require('multer');
var uploads = multer({ dest: './public/images/uploads' });




/* home page blog Post. */
router.get('/add', function(req, res, next) {
    var categoryList = db.get('categories');
    categoryList.find({},{}, function (err, categoryList) {
        /*console.log("Categories"+categories);
        categories.forEach(function(category){
            console.log(category.title);
        });*/
        res.render('addPost',{
            "title": "Add Post",
            "catList" : categoryList
        });
    });

});

router.post('/add', uploads.single('mainimage'), function(req, res, next) {
    // get form values
    var title       = req.body.title;
    var category    = req.body.category;
    var body        = req.body.body;
    var author      = req.body.author;
    var date        = new Date();
    console.log("Title"+title);
    console.log("Category"+category);
    console.log("body"+body);
    console.log("Author"+author);
    console.log("Date"+date);

    //Check for image field
    if(req.files && req.files.mainimage){
        console.log('Uploading file...');
        var mainImageOrginalName = req.files.mainimage.originalname;
        var mainImageName = req.files.mainimage.name;
        var mainImageMime = req.files.mainimage.mimetype;
        var mainImagePath = req.files.mainimage.path;
        var mainImageExt = req.files.mainimage.extension;
        var mainImageSize = req.files.mainimage.size;
    }
    else{
        console.log('mainImageFile not found....');
        var mainImageName = 'noimage.png';
    }

    //form Validations
    req.checkBody('title','Title field is required').notEmpty();
    req.checkBody('body','Body field is required').notEmpty();

    var errors = req.validationErrors();

    if(errors){
        res.render('addPost',{
            "errors": errors,
            "title" : title,
            "body" : body
        });
    }else{
        var posts = db.get('posts');

        // add it to db
        posts.insert({
            "title":title,
            "body":body,
            "category": category,
            "date":date,
            "author":author,
            "mainimage":mainImageName
        }, function (err, post) {
            if(err){
                res.send('There was an issue submitting the post');
            }else{
                req.flash('success', "Post Submitted");
                req.location('/');
                req.redirect('/');
            }
        });
    }

    res.render('addpost',{
        "title": "Add Post"
    });
});

module.exports = router;

Please help me in resolving this issues as I am stuck with this.

Thanks

via Ãkshåý Güptã