Username of a removed member looks wrong in the in-app notifications.

[SebinSong]

Problem

the username of a member who has been removed looks like below in an in-app notification content.

[ Steps to reproduce ]

1. Sign up for user 1, 2 and 3.
2. User 1 creates a group and invite user 2 and 3.
3. Kick out the user 3.
4. Check any existing in-app notification that mentions user 3, now the identity contract ID is not properly converted to the display name.

Solution

Fix it