When trying to open the Custom Color.. dialog a crash occurs with the following stacktrace:

java.lang.IllegalStateException: The window has already been closed
at com.sun.glass.ui.Window.checkNotClosed(Window.java:283)
at com.sun.glass.ui.Window.getNativeWindow(Window.java:311)
at com.sun.glass.ui.gtk.GtkWindow.getNativeWindow(GtkWindow.java:194)
at com.sun.prism.PresentableState.update(PresentableState.java:257)
at com.sun.javafx.tk.quantum.SceneState.update(SceneState.java:84)
at com.sun.javafx.tk.quantum.GlassScene.updateSceneState(GlassScene.java:264)
at com.sun.javafx.tk.quantum.GlassScene.releaseSynchronization(GlassScene.java:118)
at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2334)
at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:358)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:560)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:540)
at com.sun.javafx.tk.quantum.QuantumToolkit$15.run(QuantumToolkit.java:425)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:94)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.access$200(GtkApplication.java:47)
at com.sun.glass.ui.gtk.GtkApplication$5$1.run(GtkApplication.java:137)
at java.lang.Thread.run(Thread.java:724)

The bug is reproducible all the time.