With multi-selection mode, if a listener of selection mode cleared the last clicked item without shift-down, the item was still returned by treeView.getSelectionModel().getSelectedItem() and used as the based item for multi-selection.

1) clicked on item A,
2) clicked on item B with shift-down, at same time my listener is waked up to do some filtering, it called:
               *) treeView.getSelectionModel().clearSelection()
               *) treeView.getSelectionModel().select(B)
3) clicked on item C with shift-down
    the result was that multi-selection was done with the base item A! and A was selected.