Fix behaviour when projector is deleted

[Elblinator]

Description:
If a projector is deleted while in the projector-detail-view the user stays in the detail view of the deleted projector.

Recreation:

1. create a new projector
2. navigate into the detail view of this projector
3. delete the projector
4. you stay in the detail view
5. some elements (e.g. start/stop of the countdowns or countdown names) can still be manipulated other actions (e.g. zoom in/out) are throwning errors

Wanted behaviour:
If a projector is deleted while in the projector detail view the user should be automatically navigated into the main projector view.
The same wanted action already happens when a motion is deleted.

[emanuelschuetze]

confirmed