[SSSD] [sssd PR#5858][opened] Add check for null pointer in dp_client_register

[johanburati]

   URL: https://github.com/SSSD/sssd/pull/5858
Author: johanburati
 Title: #5858: Add check for null pointer in dp_client_register
Action: opened

PR body:
"""
Tentative fix for https://github.com/SSSD/sssd/issues/5857
"""

To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/5858/head:pr5858
git checkout pr5858