fix: make help button use subforum topics (#37741)

* fix: make help button use subforum topics

* fix: add test to check that block exists

Co-authored-by: ojeytonwilliams <ojeytonwilliams@gmail.com>

* fix: improve error message

* Update curriculum/test/test-challenges.js

Co-Authored-By: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>

client/utils/gatsby/challengePageCreator.js

@@ -61,6 +61,7 @@ const getIntroIfRequired = (node, index, nodeArray) => {
 
 exports.createChallengePages = createPage => ({ node }, index, thisArray) => {
   const {
+    block,
     fields: { slug },
     required = [],
     template,
@@ -76,6 +77,7 @@ exports.createChallengePages = createPage => ({ node }, index, thisArray) => {
     component: getTemplateComponent(challengeType),
     context: {
       challengeMeta: {
+        block: block,
         introPath: getIntroIfRequired(node, index, thisArray),
         template,
         required,