refactor(systems/gitlab): save received item count before local post-filter

src/main/java/de/hftstuttgart/unifiedticketing/systems/gitlab/GitlabFilter.java

@@ -189,6 +189,8 @@ public class GitlabFilter extends Filter<GitlabTicket, GitlabFilter>
             else throw new DeserializationException(e);
         }
 
+        lastReceivedItemCount = tr.size();
+
         logger.log(Level.FINER, "starting query post filter");
         Stream<GitlabTicketResponse> ticketStream = tr.stream();