Running WebView in NetBeans and opening some HTML page results into dozens of

java.lang.AssertionError: Unbalanced saveState/restoreState
at com.sun.webpane.sg.prism.WCGraphicsPrismContext.dispose(WCGraphicsPrismContext.java:1447)
at com.sun.webpane.sg.prism.WCPageBackBufferImpl.disposeGraphics(WCPageBackBufferImpl.java:32)
at com.sun.webpane.platform.WebPage.paint(WebPage.java:625)
at com.sun.javafx.sg.prism.NGWebView.renderContent(NGWebView.java:71)
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:1133)
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$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:317)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:150)
at com.sun.prism.render.RenderJob.run(RenderJob.java:37)
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$PipelineRunnable.run(QuantumRenderer.java:96)
at java.lang.Thread.run(Thread.java:662)