fix update paper

src/main/java/ru/ulstu/paper/service/PaperService.java

@@ -54,6 +54,9 @@ public class PaperService extends AbstractActivityService<Paper, PaperDto, Paper
     private final EventService eventService;
     private final PingService pingService;
 
+    private Paper.PaperStatus oldStatus;
+    private Set<User> oldAuthors;
+
     public PaperService(PaperRepository paperRepository,
                         FileService fileService,
                         PaperNotificationService paperNotificationService,
@@ -99,8 +102,6 @@ public class PaperService extends AbstractActivityService<Paper, PaperDto, Paper
 
     @Transactional
     public Paper update(Paper paper) {
-        Paper.PaperStatus oldStatus = paper.getStatus();
-        Set<User> oldAuthors = new HashSet<>(paper.getAuthors());
         paperRepository.save(paper);
         paperNotificationService.sendCreateNotification(paper, oldAuthors);
         paperNotificationService.statusChangeNotification(paper, oldStatus);
@@ -116,6 +117,8 @@ public class PaperService extends AbstractActivityService<Paper, PaperDto, Paper
     public PaperDto update(PaperDto paperDto) {
         Paper paper = paperRepository.findById(paperDto.getId())
                 .orElseThrow(() -> new EntityNotFoundException("Paper with id=" + paperDto.getId() + " not found"));
+        oldStatus = paper.getStatus();
+        oldAuthors = new HashSet<>(paper.getAuthors());
 
         //TODO: move to service
         if (paperDto.getFiles() != null) {