Fix paging error on loading new notifications

lib/services/notifications_manager.dart

@@ -106,12 +106,14 @@ class NotificationsManager extends ChangeNotifier {
     final pm = _buildPageManager(
       profile,
       true,
-      initialPages: [
-        PagedResponse(
-          <String>[],
-          next: PagingData(minId: highestId),
-        )
-      ],
+      initialPages: read.isEmpty && unread.isEmpty
+          ? []
+          : [
+              PagedResponse(
+                <String>[],
+                previous: PagingData(minId: highestId),
+              )
+            ],
     );
 
     final result = await (unread.isEmpty && read.isEmpty
@@ -133,7 +135,7 @@ class NotificationsManager extends ChangeNotifier {
     final pm = _buildPageManager(
       profile,
       true,
-      initialPages: read.isEmpty
+      initialPages: read.isEmpty && unread.isEmpty
           ? []
           : [
               PagedResponse(