Key '819' was not present in the dictionary error

[richardtallent-erm]

I'm trying to extract from this file:

https://apps.azsos.gov/public_services/Title_12/12-07.rtf

And getting this error:

The given key '819' was not present in the dictionary.

System.Collections.Generic.KeyNotFoundException

at RtfPipe.TextEncoding.EncodingFromCodePage(Int32 codePage) at RtfPipe.Parser.GetControlWord(String name, Int32 number) at RtfPipe.Parser.ReadControlWord() at RtfPipe.Parser.Tokens()+MoveNext() at RtfPipe.Parser.Parse() at RtfPipe.Rtf.ToHtml(RtfSource source, XmlWriter writer, RtfHtmlSettings settings) at RtfPipe.Rtf.ToHtml(RtfSource source, RtfHtmlSettings settings) at ...

Any ideas? We tried to manually add an entry for 819, but we weren't able to rebuild from the source.