Color defined as a custom CSS property crashes converter

Using the latest build 23.10, having a colour defined based on a custom CSS property causes the converter to crash with the error:
System.InvalidOperationException: ‘Operation is not valid due to the current state of the object.’

private static void ColorCustomProperty()
    const string html = "<html><body style='background-color: rgb(var(--color))' /></html>";

    using (var document = new Aspose.Html.HTMLDocument(html, "."))
        Aspose.Html.Converters.Converter.ConvertHTML(document, new PdfSaveOptions(), "out.pdf");


We have opened the following new ticket(s) in our internal issue tracking system and will deliver their fixes according to the terms mentioned in Free Support Policies.

Issue ID(s): HTMLNET-5003

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