[youdie006]

#351 made the map arm of StructData's path walker treat a missing entry as missing. The slice/array arm of the same loops (tryGetRV and Set) still calls fv.Index(index) without a bounds check, so a path into an empty slice, or a negative index, panics. That is also reachable from a struct tag alone:

                                              before                                   after
map source, Items.0.Name required, empty      required error                           required error
struct source, Items.0.Name required, empty   PANIC: reflect: slice index out of range  required error
struct tag requiredIf:Items.0.Name, empty     PANIC: reflect: slice index out of range  valid
struct source, Get("Items.-1.Name")           PANIC: reflect: slice index out of range  nil, exist=false

tryGetRV now reports an out-of-range index as missing, the same way the map source does. Set returns ErrNoField when an index that resolved earlier no longer exists, like the "entry removed before write" case #351 added for maps. Only inputs that used to panic change. A non-numeric segment still resolves to element 0 as before. I added a CHANGELOG line next to #351's.

go test ./... (under UTC and Asia/Seoul), go vet ./... and gofmt pass on Go 1.26.3. golangci-lint reports the same findings as on master.

Written with AI assistance (Claude); I have reviewed the change.