I'm getting the following NPEs (please notice they're different) when I lock the screen during CoffeeCup demo (available in apps/internal/CoffeeCup). They do not appear at specific moments and do not appear if you lock the screen for the whole demo. So I use the following:
- I run demo
- Press Ctrl-Alt-Del
- Press Escape
- repeat these until NPE is thrown.

java.lang.NullPointerException
at com.sun.scenario.effect.impl.prism.ps.PPSDrawable.create(PPSDrawable.java:54)
at com.sun.scenario.effect.impl.prism.ps.PPSRenderer.createCompatibleImage(PPSRenderer.java:146)
at com.sun.scenario.effect.impl.prism.ps.PPSRenderer.createCompatibleImage(PPSRenderer.java:60)
at com.sun.scenario.effect.impl.ImagePool.checkOut(ImagePool.java:166)
at com.sun.scenario.effect.impl.Renderer.getCompatibleImage(Renderer.java:118)
at com.sun.scenario.effect.impl.prism.ps.PPSRenderer.getCompatibleImage(PPSRenderer.java:151)
at com.sun.scenario.effect.impl.prism.ps.PPSTwoSamplerPeer.filterImpl(PPSTwoSamplerPeer.java:63)
at com.sun.scenario.effect.impl.prism.ps.PPSEffectPeer.filter(PPSEffectPeer.java:52)
at com.sun.scenario.effect.CoreEffect.filterImageDatas(CoreEffect.java:103)
at com.sun.scenario.effect.Blend.filterImageDatas(Blend.java:36)
at com.sun.scenario.effect.FilterEffect.filter(FilterEffect.java:178)
at com.sun.scenario.effect.impl.prism.PrEffectHelper.render(PrEffectHelper.java:138)
at com.sun.javafx.sg.prism.NGNode.renderClip(NGNode.java:406)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:177)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1126)
at com.sun.javafx.sg.prism.NGGroup.renderContent(NGGroup.java:187)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:185)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1126)
at com.sun.javafx.sg.prism.NGGroup.renderContent(NGGroup.java:187)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:185)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1126)
at com.sun.javafx.tk.quantum.PaintRunnable.doPaint(PaintRunnable.java:217)
at com.sun.javafx.tk.quantum.PaintRunnable.paintImpl(PaintRunnable.java:148)
at com.sun.javafx.tk.quantum.PaintRunnable.run(PaintRunnable.java:325)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:317)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:150)
at com.sun.prism.render.RenderJob.run(RenderJob.java:29)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at com.sun.javafx.tk.quantum.QuantumRenderer$ObservedRunnable.run(QuantumRenderer.java:67)
at java.lang.Thread.run(Thread.java:662)

java.lang.NullPointerException
at com.sun.prism.impl.shape.MaskData.uploadToTexture(MaskData.java:41)
at com.sun.prism.impl.ps.CachingShapeRepState$MaskCache.get(CachingShapeRep.java:214)
at com.sun.prism.impl.ps.CachingShapeRepState.render(CachingShapeRep.java:422)
at com.sun.prism.impl.ps.CachingShapeRep.fill(CachingShapeRep.java:80)
at com.sun.javafx.sg.prism.NGShape.renderContent(NGShape.java:130)
at com.sun.javafx.sg.prism.NodeEffectInput.getImageDataForBoundedNode(NodeEffectInput.java:171)
at com.sun.javafx.sg.prism.NodeEffectInput.filter(NodeEffectInput.java:74)
at com.sun.scenario.effect.FilterEffect.filter(FilterEffect.java:167)
at com.sun.scenario.effect.FilterEffect.filter(FilterEffect.java:167)
at com.sun.scenario.effect.FilterEffect.filter(FilterEffect.java:167)
at com.sun.scenario.effect.DelegateEffect.filter(DelegateEffect.java:68)
at com.sun.scenario.effect.impl.prism.PrEffectHelper.render(PrEffectHelper.java:138)
at com.sun.javafx.sg.prism.NGNode$EffectFilter.render(NGNode.java:750)
at com.sun.javafx.sg.prism.NGNode.renderEffect(NGNode.java:475)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:183)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1126)
at com.sun.javafx.sg.prism.NGGroup.renderContent(NGGroup.java:187)
at com.sun.javafx.sg.prism.NodeEffectInput.getImageDataForBoundedNode(NodeEffectInput.java:171)
at com.sun.javafx.sg.prism.NodeEffectInput.filter(NodeEffectInput.java:74)
at com.sun.scenario.effect.FilterEffect.filter(FilterEffect.java:167)
at com.sun.scenario.effect.DelegateEffect.filter(DelegateEffect.java:68)
at com.sun.scenario.effect.impl.prism.PrEffectHelper.render(PrEffectHelper.java:138)
at com.sun.javafx.sg.prism.NGNode$EffectFilter.render(NGNode.java:750)
at com.sun.javafx.sg.prism.NGNode.renderEffect(NGNode.java:475)
at com.sun.javafx.sg.prism.NGNode.renderOpacity(NGNode.java:428)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:179)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1126)
at com.sun.javafx.sg.prism.NGGroup.renderContent(NGGroup.java:187)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:185)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1126)
at com.sun.javafx.sg.prism.NGGroup.renderContent(NGGroup.java:187)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:185)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1126)
at com.sun.javafx.tk.quantum.PaintRunnable.doPaint(PaintRunnable.java:217)
at com.sun.javafx.tk.quantum.PaintRunnable.paintImpl(PaintRunnable.java:148)
at com.sun.javafx.tk.quantum.PaintRunnable.run(PaintRunnable.java:325)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:317)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:150)
at com.sun.prism.render.RenderJob.run(RenderJob.java:29)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at com.sun.javafx.tk.quantum.QuantumRenderer$ObservedRunnable.run(QuantumRenderer.java:67)
at java.lang.Thread.run(Thread.java:662)