This is a bug in 'System - GK Open Graph Article Parameters' plugin. It can't add custom tags for raw document.
Fatal error: Call to undefined method JDocumentRaw::addCustomTag() in /opt/bitnami/apps/joomla/htdocs/plugins/system/plg_gk_opengraph/plg_gk_opengraph.php on line 62
1) Is it possible to get the plugin corrected?
2) What functionality have I lost by disabling it?