Every now and then I get the exception down there (starting with JavaFX 8u40-b18 if I remember correctly)

It seems it has something to to with the fact that the items list of one of my TableViews gets cleared and so no cells are visible any more.
I will try to create a test case for this later.

java.lang.NullPointerException
at com.sun.javafx.scene.control.skin.VirtualFlow.getCellIndex(VirtualFlow.java:1726)
at com.sun.javafx.scene.control.skin.VirtualFlow.addLeadingCells(VirtualFlow.java:1274)
at com.sun.javafx.scene.control.skin.VirtualFlow.layoutChildren(VirtualFlow.java:1194)
at com.sun.javafx.scene.control.skin.VirtualFlow.setCellCount(VirtualFlow.java:231)
at com.sun.javafx.scene.control.skin.TableViewSkinBase.updateRowCount(TableViewSkinBase.java:554)
at com.sun.javafx.scene.control.skin.VirtualContainerBase.checkState(VirtualContainerBase.java:113)
at com.sun.javafx.scene.control.skin.VirtualContainerBase.layoutChildren(VirtualContainerBase.java:108)
at com.sun.javafx.scene.control.skin.TableViewSkinBase.layoutChildren(TableViewSkinBase.java:683)
at javafx.scene.control.Control.layoutChildren(Control.java:576)
at javafx.scene.Parent.layout(Parent.java:1076)
at javafx.scene.Parent.layout(Parent.java:1082)
at javafx.scene.Parent.layout(Parent.java:1082)
at javafx.scene.Parent.layout(Parent.java:1082)
at javafx.scene.Parent.layout(Parent.java:1082)
at javafx.scene.Parent.layout(Parent.java:1082)
at javafx.scene.Parent.layout(Parent.java:1082)
at javafx.scene.Parent.layout(Parent.java:1082)
at javafx.scene.Parent.layout(Parent.java:1082)
at javafx.scene.Parent.layout(Parent.java:1082)
at javafx.scene.Scene.doLayoutPass(Scene.java:552)
at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2397)
at com.sun.javafx.tk.Toolkit.lambda$runPulse$30(Toolkit.java:314)
at com.sun.javafx.tk.Toolkit$$Lambda$243/122134773.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.Toolkit.runPulse(Toolkit.java:313)
at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:340)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:525)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:505)
at com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit$400(QuantumToolkit.java:334)
at com.sun.javafx.tk.quantum.QuantumToolkit$$Lambda$41/2090707712.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)