If a route misses, AngularFireAnalytics errors

Can force this by pushing a bad route / prefix config or get multiple outlets confused, Analytics should not error, instead ignore. 

Ran into this by having `pathMatch: 'full'` on the primary outlet's root url, navigating to a non-root path on another outlet, and doing a full refresh. IMO this is an Angular bug but we should not fail in this discovered case.

`actualSnapshot` is null.