fix(client): handle builds without all challenges (#61040)

Co-authored-by: Shaun Hamilton <shauhami020@gmail.com>

client/src/pages/learn.tsx

@@ -57,7 +57,7 @@ interface LearnPageProps {
       challenge: {
         fields: Slug;
       };
-    };
+    } | null;
   };
 }
 
@@ -67,18 +67,14 @@ function LearnPage({
   isSignedIn,
   fetchState: { pending, complete },
   user,
-  data: {
-    challengeNode: {
-      challenge: {
-        fields: { slug }
-      }
-    }
-  }
+  data: { challengeNode }
 }: LearnPageProps) {
   const { name, completedChallengeCount, isDonating } = user ?? EMPTY_USER;
 
   const { t } = useTranslation();
 
+  const slug = challengeNode?.challenge?.fields?.slug || '';
+
   const onLearnDonationAlertClick = () => {
     callGA({
       event: 'donation_related',

client/src/redux/prop-types.ts

@@ -188,7 +188,6 @@ export type ChallengeNode = {
     fields: Fields;
     fillInTheBlank: FillInTheBlank;
     forumTopicId: number;
-    guideUrl: string;
     head: string[];
     hasEditableBoundaries: boolean;
     helpCategory: string;

client/src/templates/Introduction/components/super-block-intro.tsx

@@ -20,7 +20,7 @@ interface SuperBlockIntroQueryData {
         slug: string;
       };
     };
-  };
+  } | null;
 }
 
 type ReduxProps = ConnectedProps<typeof connector>;
@@ -115,13 +115,7 @@ function SuperBlockIntro({
     note: string;
   };
 
-  const {
-    challengeNode: {
-      challenge: {
-        fields: { slug: firstChallengeSlug }
-      }
-    }
-  } = useStaticQuery<SuperBlockIntroQueryData>(graphql`
+  const { challengeNode } = useStaticQuery<SuperBlockIntroQueryData>(graphql`
     query SuperBlockIntroQuery {
       challengeNode(
         challenge: {
@@ -139,6 +133,7 @@ function SuperBlockIntro({
     }
   `);
 
+  const firstChallengeSlug = challengeNode?.challenge?.fields?.slug || '';
   const {
     title: i18nSuperBlock,
     intro: superBlockIntroText,