Redirect to a 404 page when a corpus does not exist

https://redmine.teklia.com/issues/5607

In src/views/Navigation/Main.vue, the beforeRouteEnter navigation guard should show a notification and send users to the not-found page when useCorporaStore().get throws an error.

changed milestone to %Arkindex 1.7.2

added Good first bug Nice to have P3 Quick Win labels

assigned to @mlbonhomme

assigned to @erouchet and unassigned @mlbonhomme

mentioned in merge request !1838 (merged)

closed with merge request !1838 (merged)