Steps to reproduce the issue

Enable all errors reporting in php.
Add "exit()" to the end of the onContentAfterSave() method (this is for watching the error)
In the front-end, add a menu item "propose an article".
In the front-end do log as an user which can add article.
When the article is submitted, the following error is displayed:
Notice: Undefined variable: result in /home/plambotte/Public/projets/web/joomla3dev/component-factory/plugins/content/joomla/joomla.php on line 93

Expected result

No "notice" error

Actual result

Notice: Undefined variable: result in /home/plambotte/Public/projets/web/joomla3dev/component-factory/plugins/content/joomla/joomla.php on line 93

Proposed bug resolution:

Solution #1: Adding a default value for $result on the beginning of the method
Or solution #2: Add a default value for $result before the foreach (line#75)
$result = true;

System information (as much as possible)

Additional comments