CVE-2026-47753: Incus has a Nil-Pointer Dereference Panic via Instance Backup Import (volume omitted)

(*backend).CreateInstanceFromBackup in internal/server/storage/backend.go contains a nil-pointer dereference that an authenticated user with permission to create instances in any project can trigger remotely by uploading a crafted backup tarball. The Incus daemon panics and the process crashes, causing denial of service to every project on that cluster member.

This is a sibling of GHSA-fwj8-62r8-8p8m, GHSA-r7w7-mmxr-47r9, and GHSA-x5r6-jr56-89pv (all assigned 2026-05-04). Those patches added guards on adjacent fields of the same backup/config.Config struct; the Volume field on the instance-import path was missed.