Thanks, you right but we did some investigations and the error results in a bug of Joomla 3.5 in the mod_related_items

Indeed the error happens for every extension and every component other that the native Joomla content component.
They changed the code of the helper.php of the module Related items, and now if the module is published on some page linked to any other component that is not the com_content the Fatal Error is thrown.

This should be reported to the Joomla team.