Merge branch '396318-empty-string-fix-matrix-job' into 'master'

Fix pipeline marked as invalid when a variable is empty string in a parallel/matrix job

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/182993



Merged-by: Furkan Ayhan <furkanayhn@gmail.com>
Approved-by: Andrew Newdigate <andrew@gitlab.com>
Approved-by: Furkan Ayhan <furkanayhn@gmail.com>
Reviewed-by: Furkan Ayhan <furkanayhn@gmail.com>
Reviewed-by: Rajendra Kadam <rkadam@gitlab.com>
Co-authored-by: Rajendra Kadam <rkadam@gitlab.com>