Allow for null items in @DbArray lists. (#1812)

* Added code to allow for null items in @DbArray lists.

* Test case for changing OneToMany collection by editing target bean.

src/main/java/io/ebeaninternal/server/type/ScalarTypeArrayList.java

@@ -104,7 +104,8 @@ public class ScalarTypeArrayList extends ScalarTypeArrayBase<List> implements Sc
   protected List fromArray(Object[] array1) {
     List list = new ArrayList(array1.length);
     for (Object element : array1) {
-      list.add(converter.toElement(element));
+      if(element == null ) list.add(null);
+      else list.add(converter.toElement(element));
     }
     return new ModifyAwareList(list);
   }