ct_tracker: Do not call invalidate_cache if the base model does not have it
ct_tracker: Do not call invalidate_cache if the base model does not have it

nickburlett/feincms,feincms/feincms,matthiask/feincms2-content,mjl/feincms,joshuajonah/feincms,matthiask/django-content-editor,michaelkuty/feincms,michaelkuty/feincms,nickburlett/feincms,joshuajonah/feincms,mjl/feincms,michaelkuty/feincms,matthiask/feincms2-content,joshuajonah/feincms,feincms/feincms,mjl/feincms,nickburlett/feincms,matthiask/feincms2-content,joshuajonah/feincms,michaelkuty/feincms,matthiask/django-content-editor,matthiask/django-content-editor,nickburlett/feincms,matthiask/django-content-editor,feincms/feincms