Merge branch 'fix-not-null-violation-error-work-item-color' into 'master'

Fix NotNullViolation error when syncing work item color

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/152354



Merged-by: Felipe Artur <fcardozo@gitlab.com>
Approved-by: Nicolas Dular <ndular@gitlab.com>
Approved-by: Felipe Artur <fcardozo@gitlab.com>
Reviewed-by: Nicolas Dular <ndular@gitlab.com>
Co-authored-by: Eugenia Grieff <egrieff@gitlab.com>