libfdt: fdt_path_offset_namelen: Reject empty paths am: d10c84c4bc am: 9f4834b735

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/dtc/+/20024811

Change-Id: I9af6b06514f4d63de88e801714b8acf7fb71c8ff
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>