Task list + ordered list + loose list = extra newlines

Thanks to @marcel.amirault for this report.

It seems there's a rendering issue with markdown checkboxes in ordered lists, the text renders on the next line when it's a "loose list" (newlines between list items). For example, compare the rendering of these two lists in the attached GitLab screenshot:

1. [ ] Ordered list item 1.
1. [ ] Ordered list item 2.
1. [ ] Ordered list item 3.

Another list:

1. [ ] Ordered list item 1.

1. [ ] Ordered list item 2.

1. [ ] Ordered list item 3.

The issue does not exist with unordered lists:

- [ ] Unordered list item 1.
- [ ] Unordered list item 2.
- [ ] Unordered list item 3.

Another list:

- [ ] Unordered list item 1.

- [ ] Unordered list item 2.

- [ ] Unordered list item 3.