when fetching with null id return null

persist/src/main/java/lcsb/mapviewer/persist/dao/BaseDao.java

@@ -254,7 +254,10 @@ public abstract class BaseDao<T> {
    * @return object width identifier given as parameter
    */
   @SuppressWarnings("unchecked")
-  public T getById(int id) {
+  public T getById(Integer id) {
+    if (id == null) {
+      return null;
+    }
     List<?> list = getSession()
         .createQuery(" from " + this.clazz.getSimpleName() + " where id=:id " + removableAndStatemant())
         .setParameter("id", id).list();