Column headers not showing up in HTML output

[Pflanzgurke]

Hi,

it seems that the column headers are not rendered when creating tables from markdown or directly as HTML inside the markdown. I used an example which was reported on the mailing list as working. See example codelab Markdown below.

Thanks a lot for the Codelabs Tools!

summary: Table Test
id: tbtst
categories: Tests
tags: Test
status: Draft 
authors: Tobi Test
analytics account: 0

# Heading 1
## Heading 2
Duration: 2:00

The headers will be gone after rendering

<table>
<tr>
<th>Header 1</th> <th>Header 2 </th>
</tr>
<tr>
<td> Test</td> <td>Test 2</td>
</tr>
<tr>
<td>A</td><td>B</td>
</tr>
</table>

The below will miss the column headings in the generated HTML output

| Tables        | Are           | Cool  |
| ------------- |:-------------:| -----:|
| col 3 is      | right-aligned | $1600 |
| col 2 is      | centered      |   $12 |
| zebra stripes | are neat      |    $1 |

[KeyboardNerd]

Thanks for reporting the bug, Pflanzgurke!
We found the problem to be reproducible:

[C-o-d-e-C-o-w-b-o-y]

#432