Gatsby Build fails - GraphQL Error - Modular Content Fields

[drobinhood]

Gatsby fails to build if there isn't a post with at least one of the modular content fields. For instance, if DatoCmsImage isn't used in a post and only DatoCmsText is used gatsby will fail with the following query. See the following build error.

{
  allDatoCmsBlogPost {
    edges {
      node {
        title
        content {
          ... on DatoCmsText {
            text
          }
          ... on DatoCmsImage {
            image {
              url
            }
          }
        }
      }
    }
  }
}

GraphQL Error Fragment cannot be spread here as objects of type "DatoCmsText" can never be of type "DatoCmsImage".

[AdamPflug]

I believe this is essentially a duplicate of:
gatsbyjs/gatsby#3344
gatsbyjs/gatsby#4261

[stefanoverna]

Duplicate of #11