gatsby: gatsby develop ok, but gatsby build failed

Description

gatsby develop ok, but gatsby build failed

Environment

Gatsby version: 1.1.28 Node.js version: 8.9.3 Operating System: Ubuntu 16.04

File contents (if changed):

This is the source: https://github.com/aquabubu/home-gatsby

What happened:

‘gatsby develop’ ok, but ‘gatsby build’ failed.

success delete html files from previous builds — 0.174 s
success open and validate gatsby-config.js — 0.004 s
success copy gatsby files — 0.031 s
success onPreBootstrap — 0.005 s
success source and transform nodes — 0.587 s
success building schema — 0.296 s
success createLayouts — 0.009 s
success createPages — 0.524 s
success createPagesStatefully — 0.026 s
success onPreExtractQueries — 0.001 s
success update schema — 0.186 s
success extract queries from components — 0.109 s
success run graphql queries — 0.186 s
success write out page data — 0.029 s
success write out redirect data — 0.000 s
success onPostBootstrap — 0.000 s

info bootstrap finished - 3.592 s

Warning: Accessing PropTypes via the main React package is deprecated, and will be removed in  React v16.0. Use the latest available v15.* prop-types package from npm instead. For info on usage, compatibility, migration and more, see https://fb.me/prop-types-docs
Warning: Accessing createClass via the main React package is deprecated, and will be removed in React v16.0. Use a plain JavaScript class instead. If you're not yet ready to migrate, create-react-class v15.* is available on npm as a temporary, drop-in replacement. For more info see https://fb.me/react-create-class
 DONE  Compiled successfully in 11757ms                                                                                                                                                                                                                               23:05:07


You can now view aquabubu in the browser.

  http://localhost:8000/

View GraphiQL, an in-browser IDE, to explore your site's data and schema

  http://localhost:8000/___graphql

Note that the development build is not optimized.
To create a production build, use gatsby build

 WAIT  Compiling...                                                                                                                                                                                                                                                   23:05:07

 DONE  Compiled successfully in 445ms

However, gatsby build failed.

success delete html files from previous builds — 0.119 s
success open and validate gatsby-config.js — 0.005 s
success copy gatsby files — 0.020 s
success onPreBootstrap — 0.005 s
success source and transform nodes — 0.553 s
success building schema — 0.283 s
success createLayouts — 0.011 s
success createPages — 0.516 s
success createPagesStatefully — 0.025 s
success onPreExtractQueries — 0.001 s
success update schema — 0.169 s
success extract queries from components — 0.083 s
success run graphql queries — 0.027 s
success write out page data — 0.008 s
success write out redirect data — 0.001 s
success onPostBootstrap — 0.001 s

info bootstrap finished - 3.248 s

success Building CSS — 15.796 s
success Building production JavaScript bundles — 35.495 s
⠂ Building static HTML for pages
error Building static HTML for pages failed

See our docs page on debugging HTML builds for help https://goo.gl/yL9lND

  47 |     const postOverlapClass = mobile ? "post-overlap-mobile" : "post-overlap";
  48 |     const postNode = this.props.data.markdownRemark;
> 49 |     const post = postNode.frontmatter;
     |                           ^
  50 |     if (!post.id) {
  51 |       post.id = slug;
  52 |     }


  WebpackError: Cannot read property 'frontmatter' of undefined
  
  - post.js:49 PostTemplate.render
    src/templates/post.js:49:27
  
  - ReactCompositeComponent.js:796 ReactCompositeComponentWrapper._renderValidatedComponentWithoutOwnerOrContext
    ~/react-dom/lib/ReactCompositeComponent.js:796:1
  
  - ReactCompositeComponent.js:819 ReactCompositeComponentWrapper._renderValidatedComponent
    ~/react-dom/lib/ReactCompositeComponent.js:819:1
  
  - ReactCompositeComponent.js:359 ReactCompositeComponentWrapper.performInitialMount
    ~/react-dom/lib/ReactCompositeComponent.js:359:1
  
  - ReactCompositeComponent.js:255 ReactCompositeComponentWrapper.mountComponent
    ~/react-dom/lib/ReactCompositeComponent.js:255:1
  
  - ReactReconciler.js:43 Object.mountComponent
    ~/react-dom/lib/ReactReconciler.js:43:1
  
  - ReactMultiChild.js:234 ReactDOMComponent.mountChildren
    ~/react-dom/lib/ReactMultiChild.js:234:1
  
  - ReactDOMComponent.js:657 ReactDOMComponent._createContentMarkup
    ~/react-dom/lib/ReactDOMComponent.js:657:1
  
  - ReactDOMComponent.js:524 ReactDOMComponent.mountComponent
    ~/react-dom/lib/ReactDOMComponent.js:524:1
  
  - ReactReconciler.js:43 Object.mountComponent
    ~/react-dom/lib/ReactReconciler.js:43:1