FULL PRODUCT VERSION :
java version "1.8.0_66"
Java(TM) SE Runtime Environment (build 1.8.0_66-b18)
Java HotSpot(TM) 64-Bit Server VM (build 25.66-b18, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
TreeTableView's selectedItems reports include null items if deselect one item with "Ctrl".

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Steps to reproduce:

1. Run the below example.
2. Press "Ctrl"
3. Click on "Item 2"

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Method javafx.collections.ListChangeListener.Change.getList() must return selected items.
ACTUAL -
Method javafx.collections.ListChangeListener.Change.getList() returned list with null item:

Console:
1 > [null]
2 > [TreeItem [ value: Item 3 ]]

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public class Main extends Application {

	@Override
	public void start(Stage primaryStage) throws Exception {

		TreeTableView<String> treeTable = new TreeTableView<>(new TreeItem<String>("Root"));
		treeTable.getRoot().setExpanded(true);
		treeTable.getRoot().getChildren().add(new TreeItem<String>("Item 1"));
		treeTable.getRoot().getChildren().add(new TreeItem<String>("Item 2"));
		treeTable.getRoot().getChildren().add(new TreeItem<String>("Item 3"));
		treeTable.getSelectionModel().setSelectionMode(SelectionMode.MULTIPLE);
		treeTable.getSelectionModel().select(2);
		treeTable.getSelectionModel().select(3);

		TreeTableColumn<String, String> column = new TreeTableColumn<>("Text");
		column.setPrefWidth(150);
		column.setCellValueFactory(
				(CellDataFeatures<String, String> p) -> new ReadOnlyStringWrapper(p.getValue().getValue()));
		treeTable.getColumns().add(column);
		
		treeTable.getSelectionModel().getSelectedItems().addListener(new ListChangeListener<TreeItem<String>>() {

			@Override
			public void onChanged(javafx.collections.ListChangeListener.Change<? extends TreeItem<String>> change) {

				System.out.println("1 > " + change.getList());
				System.out.println("2 > " + change.getList());
			}

		});
		
		primaryStage.setScene(new Scene(new VBox(treeTable)));
		primaryStage.show();
	}

	public static void main(String[] args) {
		launch(args);
	}
}
---------- END SOURCE ----------