On release/v28, `PATCH /repos/{owner}/{repo}/milestones/{id}` with
`"due_on": null`, the documented way to remove a deadline, returns HTTP
500. The backport https://github.com/go-gitea/gitea/pull/39921 changed
`EditMilestoneOption.Deadline` to `optional.Option[*string]`, which
decodes `null` as a slice holding a nil pointer, and the go-chi/binding
validator panics on that element (`reflect: call of
reflect.Value.Interface on zero Value`).
The field has no binding rules, so tag it `form:"-"` to skip validation.
main is unaffected since https://github.com/go-gitea/gitea/pull/39528
moved the binding into Gitea.
silverwind
5aea433c71