title: GatsbyJs - How to handle empty graphql node from Contentful plugin
body: <p>I am building a site in Gatsbyjs that pulls information in via the gatsby-source-contentful plugin, but I'm struggling with the graphql side of things.</p>
  
  <p>If I have a Content model in Contentful that contains a field to override the default description for example - then if none of the content uses that yet graphql throws an error if I try to include it in my query.</p>
  
  <p>Is there anyway to short circuit the graphql queries?</p>
  
  <p><strong>Examples</strong></p>
  
  <pre><code>{
    allContentfulPage {
      edges {
        node {
          title
          description {
             description
          }
        }
      }
    }
  }
  </code></pre>
  
  <p>This will break if there is no Page model that exists with a description, but as soon as one page gets a description it works.</p>