Describe the bug
When accessing a song or setlist url that doesn't exist, there is currently a blank page shown.

Expected behavior
An info screen should be shown with a hint "The URL of the song / setlist you opened is not valid. Maybe the song / setlist was renamed. Try to search for it in the list of all songs / setlists" and a link to the list view.

• Setlist not found
• Song not found

Additional context
Holding old references in a temporary or time limited redirection collection could also be a solution.