Bug in Contacts App

There is a bug in the Contact app. Behaviour:
Go to “Contacts” --> “Search” and search a Contact. Choose one from the Fly-out-menue --> a white page is the result.
Reason: the Link is wrong.
Expect https://URL/index.php/apps/contacts/Alle Kontakte/xxxxxxxxxxxxx

But it links to https://URL/apps/contacts/Alle Kontakte/xxxxxxxxxxxxx

The “index.php” is missing.

NC 20.0.4
Contacts 3.4.2

This is the link when you use pretty URLs:

So you are perhaps running your Nextcloud with a configuration that supposes that pretty URLs are enabled…