FULL PRODUCT VERSION :
java version "1.8.0_66"
Java(TM) SE Runtime Environment (build 1.8.0_66-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.66-b17, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
When using a multiple selection mode, sometimes the list of selected items contains a null element, even though the list itself contains no null elements.

It may be a regression introduced by this fix:

http://hg.openjdk.java.net/openjfx/8u-dev/rt/rev/81af9caad4e2

REGRESSION. Last worked in version 8u60

ADDITIONAL REGRESSION INFORMATION:
java version "1.8.0_40"
Java(TM) SE Runtime Environment (build 1.8.0_40-b25)
Java HotSpot(TM) 64-Bit Server VM (build 25.40-b25, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Create a list view with 3 items "1", "2", and "3" as in the code below.
2. Select all 3 items in sequence with Ctrl-Click.
3. Deselect the 2nd item with Ctrl-Click.
4. Deselect the first item with Ctrl-Click.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The code example gives the output:

[1]
[1, 2]
[1, 2, 3]
[1, 3]
[3]
ACTUAL -
The code example gives the output:

[1]
[1, 2]
[1, 2, 3]
[1, 3]
[null]

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ListChangeListener;
import javafx.collections.ObservableList;
import javafx.scene.Scene;

import javafx.scene.control.ListView;
import javafx.scene.control.SelectionMode;
import javafx.stage.Stage;

public class ListViewSelectionIssue extends Application {
    public static void main(String[] args) {
        Application.launch(args);
    }

    @Override public void start(Stage stage) {
        ListView<String> listView = new ListView<>();
        ObservableList<String> items = FXCollections.observableArrayList();

        listView.setItems(items);
        listView.getSelectionModel().setSelectionMode(SelectionMode.MULTIPLE);

        items.addAll("1", "2", "3");
        listView.getSelectionModel().getSelectedItems().addListener((ListChangeListener<String>) c -> {
            System.out.println(listView.getSelectionModel().getSelectedItems());
        });

        Scene scene = new Scene(listView);
        stage.setScene(scene);
        stage.show();
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Call "get" on the "selected items" list elements twice, because only the first call returns null.