Obviously the issue is PD4ML-version-dependent. I tried to convert the HTML you sent with the actual version of PD4ML and did not reproduce the exception.
On the other hand the resulting PDF layout did not match the layout as it appears in the popular web browsers. Please note: despite the product name “HTML-to-PDF converter”, PD4ML is not intended for web sites capture. Our goal is on PDF side: it is to allow you to define PDF layouts of any level of complexity with a language everybody knows – HTML.