Creating PDF/A-3 document raises NPE

If I try to generate PDF/A-3 document from html I get the following exception:
```
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:744)
at com.openhtmltopdf.pdfboxout.PdfBoxFastOutputDevice.finish(PdfBoxFastOutputDevice.java:875)
at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.writePDFFast(PdfBoxRenderer.java:661)
at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.createPdfFast(PdfBoxRenderer.java:550)
at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.createPDF(PdfBoxRenderer.java:468)
at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.createPDFWithoutClosing(PdfBoxRenderer.java:395)
at com.dm.reviscan.emails.EmailToPDF.main(EmailToPDF.java:90)
```

This is a code snipped I'm using to generate PDF:
```
PdfRendererBuilder builder = new PdfRendererBuilder();
builder.usePDDocument(pdfDoc);
builder.withW3cDocument(new W3CDom().fromJsoup(htmlDoc), outFile.toURI().toURL().toString());
builder.useFastMode();
builder.useDefaultPageSize(210, 297, BaseRendererBuilder.PageSizeUnits.MM);
builder.useHttpStreamImplementation(new OkHttpStreamFactory());
builder.usePdfAConformance(PdfRendererBuilder.PdfAConformance.PDFA_3_A);
builder.usePdfVersion(1.5f);
builder.usePdfUaAccessbility(false);
builder.useFont(new File("c:\\Windows\\Fonts\\DejaVuSans.ttf"), "ArialMT");
builder.useFont(new File("c:\\Windows\\Fonts\\DejaVuSans.ttf"), "Arial-BoldMT");
builder.useFont(new File("c:\\Windows\\Fonts\\DejaVuSans.ttf"), "Times-Roman");
builder.useFont(new File("c:\\Windows\\Fonts\\DejaVuSans.ttf"), "Times-Bold");
try (InputStream colorProfile = EmailToPDF.class.getResourceAsStream("/sRGB.icc")) {
byte[] colorProfileBytes = IOUtils.toByteArray(colorProfile);
builder.useColorProfile(colorProfileBytes);
}
```
If I comment out `builder.usePdfAConformance(PdfRendererBuilder.PdfAConformance.PDFA_3_A);` document is generated, but this is not what I want.