Fix: template rev. URL error for events w/o slug
Fix: template rev. URL error for events w/o slug

In rare occasion when events don't have any deatils about them,
especially the slug, we should display event details using
`event.get_ident` as it returns either slug or ID.

shapiromatron/amy,swcarpentry/amy,wking/swc-amy,shapiromatron/amy,pbanaszkiewicz/amy,wking/swc-amy,swcarpentry/amy,vahtras/amy,shapiromatron/amy,pbanaszkiewicz/amy,pbanaszkiewicz/amy,wking/swc-amy,swcarpentry/amy,wking/swc-amy,vahtras/amy,vahtras/amy