SeriesDao.countAllStamps(): return 0 when there is no series.

Fixed displaying of index page where there is no series in database.

Exception was:
AopInvocationException: Null return value from advice does not match primitive
return type for: public abstract long ru.mystamps.web.dao.SeriesDao.countAllStamps()

Author: php-coder

src/main/java/ru/mystamps/web/dao/SeriesDao.java

@@ -37,6 +37,6 @@ public interface SeriesDao extends CrudRepository<Series, Integer> {
 	@Query("SELECT COUNT(*) FROM Series s INNER JOIN s.gibbons m WHERE m.code = :gibbonsCode")
 	int countByGibbonsNumberCode(@Param("gibbonsCode") String gibbonsNumberCode);
 
-	@Query("SELECT SUM(quantity) FROM Series")
+	@Query("SELECT COALESCE(SUM(quantity), 0) FROM Series")
 	long countAllStamps();
 }