Incorrect code block rendering when preceded by text in markdown

[iYnOtUo]

Steps to reproduce

Using flexmark to parse the following markdown:

This is a sentence.
```python
def C(m, n):
    k = 1
    l = 1

    for i in range(n):
        k *= m - i
        l *= i + 1
    return round(k / l)

The markdown should render as:

<p>This is a sentence.</p>
<pre><code class="language-python">def C(m, n):
    k = 1
    l = 1

    for i in range(n):
        k *= m - i
        l *= i + 1
    return round(k / l)
</code></pre>

Actual behavior

The code block is rendered incorrectly. The output contains unexpected nested <pre><code> tags and the formatting is broken:

<p>This is a sentence.</p>
<pre><code class="language-python">def C(m, n):
    k = 1
    l = 1
<pre><code>for i in range(n):
    k *= m - i
    l *= i + 1
return round(k / l)
</code></pre>
<p></code></pre></p>

Additional notes

• When there is no text before the code block, rendering is correct.
• The issue only appears when a line of text precedes the code block.
• Version: 0.64.8
• Code used to render:

private static String markToHTML(String markdown) {
    Parser parser = Parser.builder().build();
    HtmlRenderer renderer = HtmlRenderer.builder()
            .escapeHtml(false)
            .build();

    Node document = parser.parse(markdown);
    return renderer.render(document);
}