title: Getting TypeError becuase of undefined context
body: <p>I am trying to make a telegram bot using their apis and MTProto.
  I imported <code>telegram-mtproto</code> into my code and received an error:</p>
  
  <pre><code>ERROR in ./node_modules/telegram-mtproto/es/worker.js (./node_modules/worker-loader?inline!./node_modules/telegram-mtproto/es/worker.js)
  Module build failed (from ./node_modules/worker-loader/index.js):
  TypeError: Cannot read property 'context' of undefined
      at Object.pitch (/Volumes/Work/Work/React/Lotteo/loteo-web/node_modules/worker-loader/index.js:32:46)
   @ ./node_modules/telegram-mtproto/es/crypto.js 53:18-61
   @ ./node_modules/telegram-mtproto/es/index.js
   @ ./src/common/utils/initializers.ts
   @ ./src/common/utils/index.ts
   @ ./src/logger/rollbar.ts
   @ ./src/logger/index.ts
   @ ./src/index.tsx
   @ multi (webpack)-dev-server/client?http://0.0.0.0:3000 (webpack)/hot/dev-server.js ./src
  </code></pre>
  
  <p>Here is my code:</p>
  
  <pre><code>const MTProto = require('telegram-mtproto').default;
  const telPhone = { num : '', code: '' };
  const api = { layer : '', initConnection : '', api_id : '' };
  const server = { dev: true };
  const client = MTProto({ server, api }); 
  </code></pre>
  
  <p>I'm not sure what is wrong with it after adding <code>telegram-mtproto</code> package?</p>