userfront 로그인 후 /dashboard로 이동하게 변경

userfront/lib/features/dashboard/domain/dashboard_providers.dart

@@ -133,7 +133,8 @@ class AuthTimelineNotifier extends Notifier<AuthTimelineState> {
     if (state.isLoading || state.isLoadingMore) {
       return;
     }
-    if (state.nextCursor == null || state.nextCursor!.isEmpty) {
+    final nextCursor = state.nextCursor;
+    if (nextCursor == null || nextCursor.isEmpty) {
       return;
     }
     state = state.copyWith(isLoadingMore: true, error: null);