Fix Followers/Following list error when they contain accounts that have never posted (#38640)

app/javascript/mastodon/api_types/accounts.ts

@@ -53,7 +53,7 @@ export interface BaseApiAccountJSON {
   header_static: string;
   header_description: string;
   id: string;
-  last_status_at: string;
+  last_status_at: string | null;
   locked: boolean;
   show_media: boolean;
   show_media_replies: boolean;

app/javascript/mastodon/components/account_list_item/index.tsx

@@ -148,11 +148,15 @@ export const AccountListItem: React.FC<Props> = ({
               />
             }
           >
-            <RelativeTimestamp
-              long
-              timestamp={account.last_status_at}
-              noFuture
-            />
+            {account.last_status_at ? (
+              <RelativeTimestamp
+                long
+                timestamp={account.last_status_at}
+                noFuture
+              />
+            ) : (
+              '-'
+            )}
           </NumberFieldsItem>
         )}
         {firstVerifiedField && (

app/javascript/mastodon/features/collections/editor/accounts.tsx

@@ -61,9 +61,11 @@ const AddedAccountItem: React.FC<{
     onRemove(accountId);
   }, [accountId, onRemove]);
 
+  const lastStatusAt = account?.last_status_at;
+
   const lastPostHint = useMemo(
     () =>
-      isOlderThanAWeek(account?.last_status_at) && (
+      (!lastStatusAt || isOlderThanAWeek(lastStatusAt)) && (
         <Badge
           label={
             <FormattedMessage
@@ -75,7 +77,7 @@ const AddedAccountItem: React.FC<{
           className={classes.accountBadge}
         />
       ),
-    [account?.last_status_at],
+    [lastStatusAt],
   );
 
   return (