Infinite loop on invalid HTML

```fsharp
#r "nuget: FSharp.Data, 4.2.3"

open FSharp.Data

let content = """<html>
</html
"""

let doc = HtmlDocument.Parse(content) // Never terminates

printfn "%A" doc
```

(Different one to [previous](https://github.com/fsprojects/FSharp.Data/issues/1264))

```bash
$ dotnet --version
5.0.103
```