Columns: No blocks allowed

[henryiii]

Blocks do not render into blocks inside columns, and in fact, break the LaTeX.
Pandoc 2.0.0.1, via Brew on macOS.

Code:

---
title: Blocks in Columns
author: Henry Schreiner
date: October 31, 2017
---

# Level 2 blocks

<!--- --->

<div class="columns">
<div class="column" width="40%">
## Block one
- Item
</div>
<div class="column" width="60%">
## Block two
- Item
</div>
</div>

Compile:

pandoc -tbeamer example.md -oexample.pdf
Error producing PDF.
! Missing \endgroup inserted.
<inserted text>
                \endgroup
l.109 \end{frame}

Check output:

pandoc -tbeamer example.md

Output:

\begin{frame}{%
\protect\hypertarget{level-2-blocks}{%
Level 2 blocks}}

\begin{columns}[T]
\begin{column}{0.40\textwidth}
\hypertarget{block-one}{%
\subsection{Block one}\label{block-one}}

\begin{itemize}
\tightlist
\item
  Item
\end{itemize}
\end{column}

\begin{column}{0.60\textwidth}
\hypertarget{block-two}{%
\subsection{Block two}\label{block-two}}

\begin{itemize}
\tightlist
\item
  Item
\end{itemize}
\end{column}
\end{columns}

\end{frame}

Repeat with other numbers of ##, like one or three, and it still crashes. These are subsections, not blocks like expected. With one #, they are sections.

[trou]

Hello,
the fix is good for one case: blocks inside columns, but columns after a block are still broken.

From my MarkDown source:

## Bug example

### Block title

* item

<div class="columns">
<div class="column" width="60%">

### Inside block 1

* item 1

</div>
<div class="column" width="40%">

### Inside block 2

* item 2


</div>
</div>

outputs:

\begin{frame}{%
\protect\hypertarget{bug-example}{%
Bug example}}

\begin{block}{Block title}

\begin{itemize}
\tightlist
\item
  item
\end{itemize}

\begin{columns}[T]
\begin{column}{0.60\textwidth}
\begin{block}{Inside block 1}

\begin{itemize}
\tightlist
\item
  item 1
\end{itemize}

\end{block}
\end{column}

\begin{column}{0.40\textwidth}
\begin{block}{Inside block 2}

\begin{itemize}
\tightlist
\item
  item 2
\end{itemize}

\end{block}
\end{column}
\end{columns}

\end{block}

\end{frame}

as you can see, the top block is not closed when columns are created.