title: Error - [trust-cert] TypeError: Cannot read property 'toString' of null
body: <p>I am Building my first SharePoint client-side web part. I have used <code>gulp trust-dev-cert</code> and the output is coming with 2 errors. How to fix it?</p>
  <pre><code>C:\sharepoint&gt;gulp trust-dev-cert
  Build target: DEBUG
  [12:50:19] Using gulpfile C:\sharepoint\gulpfile.js
  [12:50:19] Starting gulp
  [12:50:19] Starting 'trust-dev-cert'...
  [12:50:19] Starting subtask 'configure-sp-build-rig'...
  [12:50:19] Finished subtask 'configure-sp-build-rig' after 5.6 ms
  [12:50:19] Starting subtask 'trust-cert'...
  [12:50:22] Error - [trust-cert] TypeError: Cannot read property 'toString' of null
  [12:50:22] Error - 'trust-cert' sub task errored after 2.59 s
   Cannot read property 'toString' of null
  [12:50:22] 'trust-dev-cert' errored after 2.93 s
  [12:50:22]
  [12:50:23] ==================[ Finished ]==================
  Error - [trust-cert] TypeError: Cannot read property 'toString' of null
  Error - 'trust-cert' sub task errored after 2.59 s
   Cannot read property 'toString' of null
  [12:50:23] Project sharepoint version:0.0.1
  [12:50:23] Build tools version:3.12.1
  [12:50:23] Node version:v10.23.0
  [12:50:23] Total duration:8.05 s
  [12:50:23] Task errors:2
  </code></pre>
  <p><a href="https://i.stack.imgur.com/G5rtu.png" rel="nofollow noreferrer">This is the content in the folder</a></p>