Download this plugin and install it, this will solve the issue.

You also can fix it by open the following file ‘/plugins/system/helix3/helix3.php’, go o line 49 you will see PHP code

JForm::addFormPath(JPATH_PLUGINS.’/system/helix3/params’);

just replace it to

JForm::addFormPath(JPATH_PLUGINS.’/system/helix3/params’);
if (is_object($data)) {
$data = (array)$data;
}

Save and recheck.