Handle markdown errors gracefully (#3468)

Co-authored-by: Nicolas Dorseuil <nicolas@gitbook.io>

Author: conico974

packages/gitbook/src/routes/markdownPage.ts

@@ -1,17 +1,35 @@
 import type { GitBookSiteContext } from '@/lib/context';
-import { throwIfDataError } from '@/lib/data';
+import { getDataOrNull } from '@/lib/data';
 import { getMarkdownForPage } from '@/lib/markdownPage';
 
 /**
  * Serve a markdown version of a page.
  * Returns a 404 if the page is not found.
  */
 export async function servePageMarkdown(context: GitBookSiteContext, pagePath: string) {
-    const result = await throwIfDataError(getMarkdownForPage(context, pagePath));
+    try {
+        const result = await getDataOrNull(getMarkdownForPage(context, pagePath));
+        if (!result) {
+            return new Response('Page not found', {
+                status: 404,
+                headers: {
+                    'Content-Type': 'text/plain; charset=utf-8',
+                },
+            });
+        }
 
-    return new Response(result, {
-        headers: {
-            'Content-Type': 'text/markdown; charset=utf-8',
-        },
-    });
+        return new Response(result, {
+            headers: {
+                'Content-Type': 'text/markdown; charset=utf-8',
+            },
+        });
+    } catch (error) {
+        console.error('Error serving markdown page:', error);
+        return new Response('Internal Server Error', {
+            status: 500,
+            headers: {
+                'Content-Type': 'text/plain; charset=utf-8',
+            },
+        });
+    }
 }