500 error when sorting project milestones by name
This happens on project milestones because there is no
name field on
It doesn't happen for group milestones because we use
MilestoneArray there instead (because we show project and group milestones).
We should probably handle this in
Milestone.sort_by_attribute rather than delegating to
Sortable. Or we could change the dropdown value.
This appears to have been introduced by https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8930.