Setup:
On a simple Stage, I register an EventHandler set to handle MouseEvents.
The EventHandler closes the stage when triggered.

Action:
I move the mouse over the Stage

Observed behaviour:
The Stage closes, but a NullPointerException is thrown.

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:29)
at com.sun.glass.ui.win.WinApplication$2$1.run(WinApplication.java:67)
at java.lang.Thread.run(Thread.java:722)

Expected behaviour:
The Stage closes. No exception is thrown.

The attached code illustrates the behaviour.