Seen while testing #40155 with core 10.11.0-rc.1

In a system, where admin, user1, and user2 exist:
User admin tries to share with "user1, user2, user1, user2"
The duplicate user2 is recognized:

Expected behaviour:

• The duplicate user1 is also recognized
• the popup never contains duplicates.

The issue is only about the preview in the popup. No errors occur (the duplicate is silently ignored) when submitting the list.