Consecutive code blocks are merged when rendering to CommonMark Markdown 1.2

When rendering to markdown/1.2, two consecutive standalone code macros without a language are rendered as indented code blocks separated by a blank line. Once parsed back, they form a single code block.

Steps to reproduce

Render the following xwiki/2.1 content to markdown/1.2 and parse it back:

{{code}}
a
{{/code}}

{{code}}
b
{{/code}}

Result

A single code macro with content a, an empty line and b.

Expected

Two code macros.