I've just started noticing this in the last week or so. The full stacktrace is as follows:

java.lang.NullPointerException
    at com.sun.javafx.geom.RectBounds.intersectWith(RectBounds.java:343)
    at com.sun.javafx.sg.prism.NGRegion.computeOpaqueRegion(NGRegion.java:351)
    at com.sun.javafx.sg.prism.NGNode.getOpaqueRegion(NGNode.java:285)
    at com.sun.javafx.sg.prism.NGNode.computeNodeRenderRoot(NGNode.java:224)
    at com.sun.javafx.sg.prism.NGRegion.computeRenderRoot(NGRegion.java:367)
    at com.sun.javafx.sg.prism.NGGroup.computeRenderRoot(NGGroup.java:360)
    at com.sun.javafx.sg.prism.NGRegion.computeRenderRoot(NGRegion.java:363)
    at com.sun.javafx.sg.prism.NGGroup.computeRenderRoot(NGGroup.java:360)
    at com.sun.javafx.sg.prism.NGGroup.computeRenderRoot(NGGroup.java:360)
    at com.sun.javafx.sg.prism.NGRegion.computeRenderRoot(NGRegion.java:363)
    at com.sun.javafx.sg.prism.NGGroup.computeRenderRoot(NGGroup.java:360)
    at com.sun.javafx.sg.prism.NGRegion.computeRenderRoot(NGRegion.java:363)
    at com.sun.javafx.sg.prism.NGGroup.computeRenderRoot(NGGroup.java:360)
    at com.sun.javafx.sg.prism.NGRegion.computeRenderRoot(NGRegion.java:363)
    at com.sun.javafx.sg.prism.NGGroup.computeRenderRoot(NGGroup.java:360)
    at com.sun.javafx.sg.prism.NGRegion.computeRenderRoot(NGRegion.java:363)
    at com.sun.javafx.sg.prism.NGGroup.computeRenderRoot(NGGroup.java:360)
    at com.sun.javafx.sg.prism.NGRegion.computeRenderRoot(NGRegion.java:363)
    at com.sun.javafx.sg.prism.NGGroup.computeRenderRoot(NGGroup.java:360)
    at com.sun.javafx.sg.prism.NGRegion.computeRenderRoot(NGRegion.java:363)
    at com.sun.javafx.sg.prism.NGGroup.computeRenderRoot(NGGroup.java:360)
    at com.sun.javafx.sg.prism.NGRegion.computeRenderRoot(NGRegion.java:363)
    at com.sun.javafx.sg.prism.NGNode.getRenderRoot(NGNode.java:142)
    at com.sun.javafx.tk.quantum.AbstractPainter.paintImpl(AbstractPainter.java:190)
    at com.sun.javafx.tk.quantum.PresentingPainter.run(PresentingPainter.java:74)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)
    at com.sun.prism.render.RenderJob.run(RenderJob.java:37)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:98)
    at java.lang.Thread.run(Thread.java:722)