title: Gatsby develop failed: Fetching SilverStripe data failed Cannot read property 'data' of undefined after setting up silverstripe-gatsby
body: <p>I am new to gatsby and was trying to test out Gatsby with Silverstripe. If it goes well, it may be great solution to one of our work project.</p>
  
  <p>I have a test silverstripe site working along which I install from the instruction available here: 
  <a href="https://github.com/unclecheese/gatsby-starter-silverstripe" rel="nofollow noreferrer">https://github.com/unclecheese/gatsby-starter-silverstripe</a></p>
  
  <p>With the instructions, My SS4.5 site is working fine as well as the endpoint /__gatsby/graphql as I am able to add query to the endpoint. </p>
  
  <p>As I tried to run "gatsby develop" as per instruction, the following errors appear and my site was not built..:</p>
  
  <p><strong>my host url is also configured in the config.js.</strong></p>
  
  <blockquote>
    <p>FetchError: invalid json response body at <a href="http://localhost/gatsbyv3/__gatsby/graphql" rel="nofollow noreferrer">http://localhost/gatsbyv3/__gatsby/graphql</a> reason: Unexpected token &lt; in JSON at position 0</p>
  </blockquote>
  
  <p>ERROR</p>
  
  <blockquote>
    <p>Fetching SilverStripe data failed Cannot read property 'data' of undefined
    TypeError: Cannot read property 'data' of undefined</p>
  </blockquote>
  
  <p>I'm not sure if I've missed anything and have not edited the config file. 
  Any help or advice would be much appreciated.
  Thank you in advance.</p>