server returns status code 500 when creating token for non-existent user (Impersonation)

[nirajacharya2]

Describe the bug

creating auth-app token for an non-existent user gives 500 status code.
https://owncloud.dev/services/auth-app/#via-impersonation-api

Steps to reproduce

1.create an auth-app token

curl -kv -XPOST 'https://localhost:9200/auth-app/tokens?expiry=72h&userName=mosss' -uadmin:admin

Expected behavior

the server should return something like 404

Actual behavior

the server return 500 status code

 TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):
< HTTP/1.1 500 Internal Server Error
< Content-Length: 0

Setup

env

OCIS_ADD_RUN_SERVICES=auth-app
AUTH_APP_ENABLE_IMPERSONATION=true

ownCloud Web UI 11.0.6
Infinite Scale 7.0.0+42014d70c0 Community