Fix trollboard crash (#2699)

I haven't tested it yet since I'm not able to reproduce the crash
locally. But by reading the code, it should work lol

Author: notmd

website/src/lib/users.ts

@@ -95,7 +95,10 @@ export const getBatchFrontendUserIdFromBackendUser = async (users: { username: s
     const account = externalAccounts.find(
       (a) => a.provider === users[userIdx].auth_method && a.providerAccountId === users[userIdx].username
     );
-    outputIds[userIdx] = account.userId;
+    // TODO check why the account is undefined
+    if (account) {
+      outputIds[userIdx] = account.userId;
+    }
   });
 
   return outputIds;