I just discovered this today, when I needed to make a minor edit to a footer template. Trying to open it resulted in the following error:
Fatal error: Uncaught Error: Call to a member function getId() on null in /home/sites/westeros.org/www/html/Scripts/ExpressionEngine/valyria/ee/EllisLab/ExpressionEngine/Controller/Design/Template.php:1125 Stack trace: #0 /home/sites/westeros.org/www/html/Scripts/ExpressionEngine/valyria/ee/EllisLab/ExpressionEngine/Controller/Design/Template.php(973): EllisLab\ExpressionEngine\Controller\Design\Template->getExistingTemplates('60') #1 /home/sites/westeros.org/www/html/Scripts/ExpressionEngine/valyria/ee/EllisLab/ExpressionEngine/Controller/Design/Template.php(281): EllisLab\ExpressionEngine\Controller\Design\Template->renderAccessPartial(Object(EllisLab\ExpressionEngine\Model\Template\Template), NULL) #2 [internal function]: EllisLab\ExpressionEngine\Controller\Design\Template->edit('624') #3 /home/sites/westeros.org/www/html/Scripts/ExpressionEngine/valyria/ee/EllisLab/ExpressionEngine/Core/Core.php(240): call_user_func_array(Array, Array) #4 /home/sites/westeros.org/www/html/Scripts/ExpressionEngine/valyria/ee/EllisLab/ in /home/sites/westeros.org/www/html/Scripts/ExpressionEngine/valyria/ee/EllisLab/ExpressionEngine/Controller/Design/Template.php on line 1125I then tested other footer templates and they all display the same behaviour. I have not found any other templates that do. Unfortunately, I cannot recall exactly what the contents may be since it was a good while since I edited one. It is not exactly the same in all of the footers, but there are common elements.
On the site, the footers display correctly.
ExpressionEngine implements Markdown Extra and BBCode. Please see the Markdown Extra docs and the BBCode Wikipedia article for a full reference.
**bold**, __bold__, *italics*, _italics_, ~strike/del~, `code()`
bold, italics, strike/del, code()
Link: [link title](https://example.com)
Image: 
[blockquote]...[/blockquote], [quote]...[/quote], and Markdown style:
> Some quoted text. > > This is all one quote.
[code]...[/code], and you can also specify the language for syntax highlighting, [code=php]...[/code]
GitHub flavored Markdown code fences are also supported:
```
public function decoderRing($str)
{
return str_rot13($str);
}
```