title: Error: Type with name "AuthorYaml" does not exists - gatsby-casper starter
body: <p>I'm trying to build a gatsby website based on gatsby-casper starter but I am getting a hard to debug error related to the graphql schema. The error I get is this:</p>
  <pre><code>Error: Type with name &quot;AuthorYaml&quot; does not exists
  
  - TypeStorage.js:44 SchemaComposer.get
  [Physicc-blog]/[graphql-compose]/lib/TypeStorage.js:44:13
  
  - TypeMapper.js:585 ThunkComposer._thunk
  [Physicc-blog]/[graphql-compose]/lib/TypeMapper.js:585:34
  
  - ThunkComposer.js:20 ThunkComposer.get ofType [as ofType]
  [Physicc-blog]/[graphql-compose]/lib/ThunkComposer.js:20:34
  
  - ThunkComposer.js:46 ThunkComposer.getType
  [Physicc-blog]/[graphql-compose]/lib/ThunkComposer.js:46:17
  
  - ListComposer.js:22 ListComposer.getType
  [Physicc-blog]/[graphql-compose]/lib/ListComposer.js:22:49
  
  - ObjectTypeComposer.js:348 ObjectTypeComposer.getFieldConfig
  [Physicc-blog]/[graphql-compose]/lib/ObjectTypeComposer.js:348:18
  
  - index.js:220 forEach
  [Physicc-blog]/[gatsby]/src/schema/extensions/index.js:220:48
  
  - Array.forEach
  
  - index.js:215 forEach
  [Physicc-blog]/[gatsby]/src/schema/extensions/index.js:215:8
  
  - Array.forEach
  
  - index.js:211 processFieldExtensions
  [Physicc-blog]/[gatsby]/src/schema/extensions/index.js:211:32
  
  - schema.js:226 processTypeComposer
  [Physicc-blog]/[gatsby]/src/schema/schema.js:226:11
  
  - schema.js:200 map
  [Physicc-blog]/[gatsby]/src/schema/schema.js:200:7
  
  - Array.map
  
  - schema.js:199 updateSchemaComposer
  [Physicc-blog]/[gatsby]/src/schema/schema.js:199:50
  
  - schema.js:64 buildSchema
  [Physicc-blog]/[gatsby]/src/schema/schema.js:64:3
  </code></pre>
  <p>I have used</p>
  <pre><code>gatsby new my-gatsby-project https://github.com/scttcper/gatsby-casper
  </code></pre>
  <p>to initialize the project. I'm unable to figure out why this error is being generated.</p>