controller.spawn() throws UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'context' of undefined

[NxP4Code]

Steps to reproduce
Run the following sample code (https://hazel-jazzy-peach.glitch.me/):

//  __   __  ___        ___
// |__) /  \  |  |__/ |  |  
// |__) \__/  |  |  \ |  |  

// This is the main file for the starter-webex bot.

// Import Botkit's core features
const { Botkit } = require('botkit');
const { BotkitCMSHelper } = require('botkit-plugin-cms');

// Import a platform-specific adapter for webex.

const { WebexAdapter } = require('botbuilder-adapter-webex');

const { MongoDbStorage } = require('botbuilder-storage-mongodb');
const common = require('./common');


// Load process.env values from .env file
require('dotenv').config();

let storage = null;
if (process.env.MONGO_URI) {
    storage = new MongoDbStorage({
        url : process.env.MONGO_URI,
    });
}


const adapter = new WebexAdapter({
    // REMOVE THIS OPTION AFTER YOU HAVE CONFIGURED YOUR APP!
    enable_incomplete: true,
  
    access_token: process.env.access_token,
    public_address: process.env.public_address,
    secret: process.env.secret
})    


const controller = new Botkit({
    webhook_uri: '/api/messages',

    adapter: adapter,

    storage
});

controller.spawn().then(bot => {
    common.bot = bot;
     bot.api.messages.create({
       text: "beep, boop!",
       toPersonEmail: '[email protected]'

     });
  });

if (process.env.cms_uri) {
    controller.usePlugin(new BotkitCMSHelper({
        cms_uri: process.env.cms_uri,
        token: process.env.cms_token,
    }));
}

controller.usePlugin({
  name: 'webserver logger',
  init: function(botkit) {
    console.log('binding new express middleware');
    botkit.webserver.use(function(req, res, next) {
      console.log('FIRE MIDDLEWARE');
      console.log('> ', req.url, JSON.stringify(req.body, null, 2));
      next();
    });
  }
});

// Once the bot has booted up its internal services, you can use them to do stuff.
controller.ready(() => {

    // load traditional developer-created local custom feature modules
    controller.loadModules(__dirname + '/features');

    /* catch-all that uses the CMS to trigger dialogs */
    if (controller.plugins.cms) {
        controller.on('message,direct_message', async (bot, message) => {
            let results = false;
            results = await controller.plugins.cms.testTrigger(bot, message);

            if (results !== false) {
                // do not continue middleware!
                return false;
            }
        });
    }

});

controller.webserver.get('/', (req, res) => {
    res.send(`This app is running Botkit ${ controller.version }.`);
});

Expected behavior:
No error generated, and an instance of the bot can be used to call bot.api.messages.create function.

Even with this error bot responds to added features.

Describe your issue here, include as much detail as necessary to reproduce the issue or implement a missing functionality.

• Botkit version: 4.8.1
• Messaging Platform: WebEx
• Node version: 12.13
• Os: Windows
• Any other relevant information: Glitch URL: https://hazel-jazzy-peach.glitch.me/
  -I had a chat with @benbrown and this bug is acknowledged. This bug is related to line
  

  botkit/packages/botkit/src/core.ts

  Line 1080 in 77e309b

  const adapter = custom_adapter || (config.context && config.context.adapter) ? config.context.adapter : this.adapter;

[benbrown]

Fixed in 4.9