fix(gatsby-source-contentful): handle nullable fields (#38358)

Author: derrysucari

packages/gatsby-source-contentful/rich-text.d.ts

@@ -10,8 +10,8 @@ interface ContentfulRichTextGatsbyReference {
 }
 
 interface RenderRichTextData<T extends ContentfulRichTextGatsbyReference> {
-  raw: string
-  references: T[]
+  raw?: string | null
+  references?: T[] | null
 }
 
 export function renderRichText<

packages/gatsby-source-contentful/src/rich-text.js

@@ -3,7 +3,7 @@ import { documentToReactComponents } from "@contentful/rich-text-react-renderer"
 import resolveResponse from "contentful-resolve-response"
 
 export function renderRichText({ raw, references }, options = {}) {
-  const richText = JSON.parse(raw)
+  const richText = JSON.parse(raw || null)
 
   // If no references are given, there is no need to resolve them
   if (!references || !references.length) {