ADDITIONAL SYSTEM INFORMATION :
Windows 7 64bit, Java 11.0.2

A DESCRIPTION OF THE PROBLEM :
If double click is performed on an empty space (where no columns and rows are rendered) it triggers NullPointerException

Stacktrace:

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at javafx.controls/com.sun.javafx.scene.control.behavior.TreeTableRowBehavior.handleClicks(TreeTableRowBehavior.java:89)
at javafx.controls/com.sun.javafx.scene.control.behavior.CellBehaviorBase.simpleSelect(CellBehaviorBase.java:285)
at javafx.controls/com.sun.javafx.scene.control.behavior.TableRowBehaviorBase.doSelect(TableRowBehaviorBase.java:119)
at javafx.controls/com.sun.javafx.scene.control.behavior.CellBehaviorBase.mousePressed(CellBehaviorBase.java:176)
at javafx.controls/com.sun.javafx.scene.control.behavior.TableRowBehaviorBase.mousePressed(TableRowBehaviorBase.java:63)
at javafx.controls/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274)
at javafx.base/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3851)
at javafx.graphics/javafx.scene.Scene$MouseHandler.access$1200(Scene.java:3579)
at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1849)
at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2588)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:397)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:434)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:390)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:433)
at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:556)
at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:942)
at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
at java.base/java.lang.Thread.run(Thread.java:834)


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Start the application
3. The tree table should have at leas one column and one row displayed.
2. double click on the empty space., where no row and column are rendered.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
NullPointerException should not be triggered.
ACTUAL -
It happens every time when the user double clicks on the empty space

---------- BEGIN SOURCE ----------
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeTableColumn;
import javafx.scene.control.TreeTableRow;
import javafx.scene.control.TreeTableView;
import javafx.scene.input.MouseEvent;
import javafx.stage.Stage;

public class TreeTableViewNPE extends Application {

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

TreeTableView<Object> treeTableView = new TreeTableView<>();
TreeTableColumn<Object, ?> treeTableColumn = new TreeTableColumn<>();
treeTableView.getColumns().add(treeTableColumn);
treeTableView.setRoot(new TreeItem<>(new Object()));

primaryStage.setScene(new Scene(treeTableView));
primaryStage.show();
}

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

CUSTOMER SUBMITTED WORKAROUND :
Set a rowFactory for the table, and add an EventFilter to the row, where the event is consumed if the current item is null and the click count is even:

treeTableView.setRowFactory(rf -> {
TreeTableRow<Object> row = new TreeTableRow<>();
row.addEventFilter(MouseEvent.MOUSE_PRESSED, event -> {
if (row.getItem() == null && event.getClickCount() % 2 == 0) {
event.consume();
}
});
return row;
});


FREQUENCY : always