我有一个非常简单的盖茨比应用程序。我正在运行gatsby Development，它工作良好，但当我运行gatsby build时，我得到了一个错误。我不知道为什么开发能工作，而构建不能。不知道我错过了什么！

import React from "react"

import Layout from "./layout"

const ProductTemplate = ({ pageContext }) => {
const { product } = pageContext
return (
  <Layout>
    <h1>{product.title}</h1>
    <div>{product.description}</div>

  </Layout>
  )
}

export default ProductTemplate

这是确切的错误

   8 |   return (
   9 |     <Layout>
> 10 |       <h1>{product.title}</h1>
     |                    ^
  11 |       <div>{product.description}</div>
  12 | 


  WebpackError: TypeError: Cannot read property 'title' of undefined

  - product.js:10 
  src/pages/product.js:10:20

gatsby-node.js

const path = require(`path`)
exports.createPages = async ({ graphql, actions }) => {
const { createPage } = actions
// Query for all products in Shopify
const result = await graphql(`
  query {
    allShopifyProduct(sort: { fields: [title] }) {
      edges {
        node {
          title
          shopifyId
          handle
          description
          availableForSale
          priceRange {
            maxVariantPrice {
              amount
            }
            minVariantPrice {
              amount
            }
          }
        }
      }
    }
  }
`)
// Iterate over all products and create a new page using a template
// The product "handle" is generated automatically by Shopify
result.data.allShopifyProduct.edges.forEach(({ node }) => {
  createPage({
    path: `/product/${node.handle}`,
    component: path.resolve(`./src/pages/product.js`),
    context: {
      product: node,
    },
  })
})
}