NPE inside javafx runtime makes javafx stop rendering. Here's the exception:

You can reproduce this by:
1) installing Modellus X 0.2. Download from: "http://modellus.co/index.php/download"
2) Download "hk.modellus" from "http://modellus5.googlecode.com/issues/attachment?aid=5950002000&name=hk.modellus&token=qx3YvRfDJJSyeQdI2rqdygnzyqk%3A1357357146872" and open with Modellus
3) press play inside Modellus

java.lang.NullPointerException
at com.sun.javafx.sg.prism.NGCanvas$RenderBuf.validate(NGCanvas.java:76)
at com.sun.javafx.sg.prism.NGCanvas.initCanvas(NGCanvas.java:336)
at com.sun.javafx.sg.prism.NGCanvas.renderContent(NGCanvas.java:316)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:187)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1145)
at com.sun.javafx.sg.prism.NGGroup.renderContent(NGGroup.java:204)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:187)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1145)
at com.sun.javafx.sg.prism.NGGroup.renderContent(NGGroup.java:204)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:187)
at com.sun.javafx.sg.prism.NGNode.doRender(NGNode.java:39)
at com.sun.javafx.sg.BaseNode.render(BaseNode.java:1145)
at com.sun.javafx.tk.quantum.EmbeddedPainter.doPaint(EmbeddedPainter.java:116)
at com.sun.javafx.tk.quantum.AbstractPainter.paintImpl(AbstractPainter.java:181)
at com.sun.javafx.tk.quantum.EmbeddedPainter.run(EmbeddedPainter.java:91)
at java.util.concurrent.Executors$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)