RoundtripRenderer looses list content

[stylefish]

hi,

i've an issue when using the RoundtripRenderer. When this document gets parsed and rendered back to md (doing this for cleanup), the first list element is missing:

here is some sample code:

var md = @"1. 1. 

2. 2. 

3. 3. 

- 1. 

- 2. 
";
var parsed = Markdown.Parse(md, true);
var w = new StringWriter();
var r = new RoundtripRenderer(w);
r.Render(parsed);
w.Flush();
var md2 = w.ToString();

Console.WriteLine(md2);

md and md2 should be equal, but md2 is missing the 1. after the first dash -.

so this:

1. 1. 

2. 2. 

3. 3. 

- 1. 

- 2. 

is after the rpundtrip this:

1. 1. 

2. 2. 

3. 3. 

- 

- 2. 

according to commonmark reference implementation this should work: https://spec.commonmark.org/dingus/

is this a bug or is there a way to workaround this? i'm a little stuck here.

any help would be much appreciated! thank you! greetings

[MihaZupan]

Probably a bug in the roundtrip renderer for ordered lists. Compare the ordered part https://github.com/xoofx/markdig/blob/682c727288defba5dfab05ccb4ef847c760d412c/src/Markdig/Renderers/Roundtrip/ListRenderer.cs#L30-L32 vs unordered https://github.com/xoofx/markdig/blob/682c727288defba5dfab05ccb4ef847c760d412c/src/Markdig/Renderers/Roundtrip/ListRenderer.cs#L47-L58

The former is probably missing the handling for 0 blocks & the pop indent.

[stylefish]

great - thanks for pointing that out - i'll have a look next week and try to create a PR