NullPointerException on using column-count feature

When using column-count in CSS i am getting the following error on version 1.0.10. Tested with example [columns-floats-unbalanced.](https://github.com/danfickle/openhtmltopdf/blob/ccd29f03ede2aecadac9c39fda95a5fedfb23645/openhtmltopdf-examples/src/main/resources/visualtest/html/text/columns-floats-unbalanced.html). Is that a problem with my version?

`Exception in thread "main" java.lang.NullPointerException
at org.apache.pdfbox.cos.COSArray.add(COSArray.java:62)
at com.openhtmltopdf.pdfboxout.PdfBoxAccessibilityHelper.finishNumberTree(PdfBoxAccessibilityHelper.java:858)
at com.openhtmltopdf.pdfboxout.PdfBoxFastOutputDevice.finish(PdfBoxFastOutputDevice.java:908)
at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.writePDFFast(PdfBoxRenderer.java:674)
at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.createPdfFast(PdfBoxRenderer.java:564)
at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.createPDF(PdfBoxRenderer.java:490)
at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.createPDF(PdfBoxRenderer.java:427)
at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.createPDF(PdfBoxRenderer.java:409)
at com.openhtmltopdf.pdfboxout.PdfRendererBuilder.run(PdfRendererBuilder.java:46)
at com.dotcloud.openhtmltopdfrunner.PdfBuilder.generate(PdfBuilder.java:139)
at com.dotcloud.openhtmltopdfrunner.OpenHTMLtoPDFRunner.main(OpenHTMLtoPDFRunner.java:29)`