* gitlab_hook: use empty string for non-existent attr in gitlab API response;
* gitlab_hook: use None for non-existent attr in gitlab API response;
* gitlab_hook: use None for non-existent attr in gitlab API response - add changelog fragment;
* gitlab_hook: update changelog fragment for #4668
* Update changelogs/fragments/4668-gitlab_hook-use-None-for-non-existent-attr.yml
Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit da2dfd0706)
Co-authored-by: Kirill Petrov <crw.inbox@gmail.com>