Error on null nested properties

[mattgolem]

The Exporter 2.0.2 go to error when the column of the grid has nested property ("town.name" for example) and first property is null (town == null for example). The vaadin grid 8.9.3 permits it with NestedNullBehavior.ALLOW_NULLS option:

example:
column = grid.addColumn("town.name", renderer, NestedNullBehavior.ALLOW_NULLS);