Blockquote and List don't support nesting

Blockquote and list have two problems working with nested elements.
If there are two line breaks, elements gets duplicated outside the blockquote;

```
List

1. Item

2. Item
```

The same occurs if other elements are nested, but the inner version returns as `undefined`;
```
> # Title
> Some text
>
> More Text
```

No source file or test is named. Reproduce the two examples in the repository's markdown-to-React parsing path, then trace how blockquotes and lists handle nested elements and blank lines. Done means nested content is retained once, without duplication or undefined output.

Written by the indexing model from the issue text.