made sure that movies and news don't do stupid stuff around requestin…

…g `oldestDateAt`

The bug occurs because
- `timestamp.Timestamp.GetSeconds()` -> Seconds since the Epoch
- `time.Time.Second()` -> Second since last whole minute

=> checking if the `oldestDateAt` is empty needs to change accordingly

server/backend/movie.go

@@ -52,7 +52,7 @@ func (s *CampusServer) getMovies(ctx context.Context, lastID int32, oldestDateAt
 	tx := s.db.WithContext(ctx).
 		Joins("File").
 		Order("date ASC")
-	if oldestDateAt.Second() != 0 || oldestDateAt.Nanosecond() != 0 {
+	if !oldestDateAt.IsZero() {
 		tx = tx.Where("date > ?", oldestDateAt)
 	}
 	if err := tx.Find(&movies, "kino > ?", lastID).Error; err != nil {

server/backend/news.go

@@ -97,7 +97,7 @@ func (s *CampusServer) getNews(ctx context.Context, sourceID int32, lastNewsID i
 	if sourceID != 0 {
 		tx = tx.Where("src = ?", sourceID)
 	}
-	if oldestDateAt.Second() != 0 || oldestDateAt.Nanosecond() != 0 {
+	if !oldestDateAt.IsZero() {
 		tx = tx.Where("date > ?", oldestDateAt)
 	}
 	if lastNewsID != 0 {